Build material container

ABSTRACT

Certain examples of a build material container for a three-dimensional printing system is described. The build material container has an external casing and an internal compartment within the external casing. The internal compartment may have a reservoir to store build material, where the reservoir has a channel structure, and a surround that encloses the reservoir. A partition is provided within which the channel structure is mounted, the partition forming an upper surface of the internal compartment and being independent from the external casing and the surround. The partition restricts access to the internal compartment and collects build material during use of the channel structure.

BACKGROUND

Additive manufacturing techniques, such as three-dimensional printing,relate to techniques for making three-dimensional objects of almost anyshape from a digital three-dimensional model through additive processes.In these processes, three-dimensional objects are generated on alayer-by-layer basis under computer control. A large variety of additivemanufacturing technologies have been developed, differing in buildmaterials, deposition techniques and processes by which thethree-dimensional object is formed from the build material. Suchtechniques may range from applying ultraviolet light to photopolymerresin build material, to melting semi-crystalline thermoplastic buildmaterials in powder, or powder-like, form, to electron-beam melting ofmetal powder build material. Other examples of build material includeshort fiber build material.

Additive manufacturing processes usually begin with a digitalrepresentation of a three-dimensional object to be manufactured. Thisdigital representation is virtually sliced into slices by computersoftware or may be provided in pre-sliced format. Each slice representsa cross-section of the desired object. In some examples, the slices aresent to an additive manufacturing apparatus, which in some instances isknown as a three-dimensional printer. In other examples, slicing isperformed by the three-dimensional printer. In powder-based 3D printingsystems the 3D printer forms successive layers of build material on abuild platform and each layer is selectively solidified, based on thereceived slice data. This process is repeated until the object iscompleted, thereby building the object layer-by-layer. Other 3D printingtechnologies may form objects in a different manner, for example bydirectly depositing material based on the slice data.

The build material from which the object is manufactured may varydepending on the manufacturing technique and may for example comprisedry powders or powder-like material.

BRIEF DESCRIPTION OF THE DRAWINGS

Various example features will be apparent from the detailed descriptionwhich follows, taken in conjunction with the accompanying drawings,wherein:

FIGS. 1A to 1C are schematic cross sections showing an example buildmaterial container and reservoir;

FIGS. 1D to 1F are schematic cross sections showing examples of a buildmaterial reservoir;

FIGS. 1G to 1I are schematic cross sections showing examples of asupport structure within a build material container;

FIGS. 2A and 2B are schematic drawings showing example three-dimensionalprinting systems;

FIGS. 3A to 3D are schematic cross sections showing example buildmaterial containers with load bearing elements and stiffening members;

FIGS. 3E to 3F are schematic top views showing example build materialcontainers with load bearing elements and stiffening members;

FIG. 3G is a schematic view of a kit according to an example;

FIG. 4A is a flow diagram showing an example method for making a buildmaterial container;

FIG. 4B is a flow diagram showing an example method for constructing abuild material container;

FIG. 5 is a schematic drawing showing an example blank or net for abuild material container;

FIG. 6A is a schematic cross section showing an example build materialcontainer having a removal portion;

FIG. 6B is a schematic isometric drawing of the example build materialcontainer of FIG. 6A;

FIGS. 6C to 61 are schematic drawings of example structurally-weakenedportions of an external casing;

FIG. 7 is a schematic drawing showing an example blank or net for abuild material container having removable portions;

FIG. 8A is a flow diagram showing an example method for manufacturing abuild material container;

FIG. 8B is a flow diagram showing an example method for opening a buildmaterial container;

FIGS. 9A to 9C are schematic cross sections showing example buildmaterial containers with partitions;

FIG. 9D is a schematic isometric drawing of an example partition;

FIGS. 9E to 9F are schematic cross sections showing additional examplebuild material containers with partitions;

FIG. 10A is a flow diagram showing an example method for assembling abuild material container;

FIG. 10B is a flow diagram showing an example method for filling a buildmaterial container;

FIG. 11A is a schematic cross section of an example gas inlet structure;

FIGS. 11B to 11G are schematic cross sections of an example buildmaterial reservoir during use;

FIGS. 11H to 11J are further schematic cross sections of example gasinlet structures;

FIG. 12 is a flow diagram showing an example method for supplying buildmaterial in a three-dimensional printing system;

FIGS. 13A to 13C are schematic cross sections of an example buildmaterial container comprising multiple container cells;

FIG. 13D is a schematic diagram of a support element for multiplecontainer cells;

FIG. 14 is a flow diagram showing an example method for filling a buildmaterial container;

FIGS. 15A and 15B are respective front and lateral cross sections of anexample build material container; and

FIG. 16 is an isometric view showing how an example build materialcontainer may be constructed.

DETAILED DESCRIPTION

Three-dimensional objects can be generated using additive manufacturingtechniques. The objects may be generated by solidifying portions ofsuccessive layers of build material. The build material can bepowder-based and the properties of generated objects may be dependentupon the type of build material and the type of solidification. In someexamples, solidification of the powder material is enabled using aliquid binding agent, such as an adhesive. In further examples,solidification may be enabled by temporary application of energy to thebuild material, for example using a focused laser beam. In certainexamples, liquid fusing agents are applied to build material, wherein afusing agent is a material that, when a suitable amount of energy isapplied to a combination of build material and fuse agent, causes thebuild material to heat up, to melt, fuse and solidify. Other agents mayalso be used, e.g. agents that inhibit or modify a level of fusing whenselectively deposited in certain areas. In other examples, other buildmaterials and other methods of solidification may be used. In certainexamples, the build material includes paste material, slurry material orliquid material. Certain examples presented herein describe examples ofbuild material containers which contain and deliver build material tothe additive manufacturing process. In examples, the build material maybe dry, or substantially dry, powder.

In one example the build material used in the additive manufacturingprocess of this disclosure is a powder that has an average volume-basedcross-sectional particle diameter size of between approximately 5 andapproximately 400 microns, between approximately 10 and approximately200 microns, between approximately 15 and approximately 120 microns orbetween approximately 20 and approximately 70 microns. Other examples ofsuitable, average volume-based particle diameter ranges includeapproximately 5 to approximately 70 microns, or approximately 5 toapproximately 35 microns. In this example a volume-based particle sizeis the size of a sphere that has the same volume as the powder particle.With “average” it is intended to explain that most of the volume-basedparticle sizes in the container are of the mentioned size or size rangebut that the container may also contain particles of diameters outsideof the mentioned range. For example, the particle sizes may be chosen tofacilitate distributing build material layers having thicknesses ofbetween approximately 10 and approximately 500 microns, or betweenapproximately 10 and approximately 200 microns, or between approximately15 and approximately 150 microns. One example of an additivemanufacturing system may be pre-set to distribute build material layersof approximately 80 microns using build material containers that containpowder having average volume-based particle diameters of betweenapproximately 40 and approximately 60 microns. For example, the additivemanufacturing apparatus can be configured or controlled to form powderlayers having different layer thicknesses.

Suitable powder-based build materials for use in example containers ofthis disclosure include at least one of polymers, crystalline plastics,semi-crystalline plastics, polyethylene (PE), polylactic acid (PLA),acrylonitrile butadiene styrene (ABS), amorphous plastics, PolyvinylAlcohol Plastic (PVA), Polyamide, thermo(setting) plastics, resins,transparent powders, colored powders, metal powder, ceramics powder suchas for example, glass particles, and/or a combination of at least two ofthese or other materials, wherein such combination may include differentparticles each of different materials, or different materials in asingle compound particle. Examples of blended build materials includealumide, which may include a blend of aluminum and polyamide,multi-color powder, and plastics/ceramics blends. Blended build materialmay comprise two or more different respective average particle sizes.

As noted above, in other examples, the build material comprises fibers.These fibers may for example be formed by cutting extruded fibers intoshort lengths. The length may be selected to allow effective spreadingof the build material onto a build platform. For example, the length maybe approximately equal to the diameter of the fibers.

A particular batch of build material for use in an additivemanufacturing process may be “virgin” build material or “used” buildmaterial. Virgin build material should be considered to be buildmaterial which has not previously been used in any part of an additivemanufacturing process, and/or which has not passed through any part of athree-dimensional printing system. An unopened supply of build materialas supplied by a build material manufacturer may therefore containvirgin build material. By contrast, used build material is buildmaterial which has previously been supplied to a three-dimensionalprinting system for use in an additive manufacturing process but whichhas not been solidified during the process. For example, the used buildmaterial may be produced during a thermal-fusing, three-dimensionalprinting operation, in which powder build material is heated to close toits melting temperature for a period of time which may be sufficient tocause material degradation of the powder. In this respect, it will beunderstood that not all of the build material supplied to athree-dimensional printing system for use in an additive manufacturingprocess may be used and/or incorporated into a three-dimensional printedarticle. At least some of the non-solidified build material recoveredduring or after completion of a 3D print job may be suitable for reusein a subsequent additive manufacturing process. Such build material maybe stored, for example internally or externally, to the threedimensional printing system for subsequent use. The used build materialmay be mixed with virgin build material for subsequent printingroutines. The mixing proportion may be variable, for example based onpowder properties. In one example, a mix of 80% used and 20% virginbuild material may be used for prototyping, with 100% virgin buildmaterial being used for critical objects. In another example, a mix of80% used and 20% virgin powder is used for production parts, with ahigher proportion of used powder being used for prototyping. Buildmaterial containers may be used to supply recycled or reconditioned(i.e. used but unsolidified) build material in addition to, or insteadof, virgin (i.e. unused) build material. In certain cases, buildmaterial of varying qualities may be supplied, e.g. different buildmaterial reservoirs may supply different grades of build material thateach adhere to different quality specifications. In some examples, usedbuild material is returned to a supplier of build material. The suppliermay then provide reconditioned used build material, or a mixture ofreconditioned used build material and virgin build material, at a lowercost than pure virgin build material. Different grades of build materialmay be adapted for different uses, e.g. recycled or reconditioned buildmaterial may be used for prototyping, and build material with a largeproportion of virgin build material (e.g. greater than 50-80%) may beused for production.

Certain examples described herein provide ways to supply build materialto a three-dimensional printing system, e.g. a three-dimensional printeror build material processing station for a three-dimensional printer.Certain examples are directed towards build material containers andreservoirs that allow build material to be transported betweenlocations, and stored until use. Certain examples are particularlysuited to holding and storing large volumes of build material, e.g. forhigh throughput additive manufacturers. Certain examples enable largevolumes (e.g. around 1-2 m³) of build material to be safely filled,transported and supplied. Certain examples are also designed to berecyclable and to minimize waste.

FIGS. 1A to 1I introduce a set of structures that may be used,individually or in combination, to form a build material container.

FIGS. 1A to 1C show certain aspects of a build material containeraccording to examples.

FIG. 1A schematically shows a build material container 101 thatcomprises an external casing 110 and an internal space or compartment111 for receiving a build material reservoir. A cross section of theexternal casing 110 is shown. The external casing 110 may be anythree-dimensional shape. It may be polyhedral, such a cuboid, a prism,or a pyramid. It may be constructed from a variety of materialsincluding, amongst others, corrugated media or board, polymers, andmolded natural fibers.

FIG. 1B schematically shows a cross-section of a build materialreservoir 112 or sub-container according to an example. The reservoir112 is configured to fit into an internal space 111 of an externalcasing 110. In use, the build material reservoir 112 holds or storesbuild material, e.g. of the form described above. As such, the externalcasing in the present example is “external” with reference to the buildmaterial reservoir (e.g. is outside said reservoir). In certainexamples, the external casing described herein may be packaged withinadditional casing or packaging, e.g. additional containers for shippingand/or wrapped in protective film.

The build material reservoir 112 may comprise a container with a channelstructure 113 to allow access to the build material. The container maybe sealed before use. The channel structure 113 may comprise an outletstructure for extracting build material from the build materialreservoir 112 or an inlet structure for supplying build material to thebuild material reservoir 112. In one case, a build material reservoir112 may comprise multiple access channels, e.g. an outlet structure andan inlet structure. In certain cases, the build material reservoir 112may also comprise gas flow valves, e.g. to let a gas into or out of thereservoir. Although the build material reservoir 112 has a squarecross-section indicating a cubic structure in this example, it may haveany three-dimensional shape, e.g. a rigid polyhedral arrangement orflexible bag-like structure. Similarly, the channel structure 113 isshown at the top of the build material reservoir 112 for ease ofexample, it may be located in another location in other examples.

FIG. 1C schematically shows a cross-section of a build materialreservoir 112 mounted within an external casing 110. The build materialreservoir 112 may be structured to fit within the dimensions of theexternal casing 110. In one example, the upper portions 114 of theexternal casing 110 may be foldable to provide an outer surface of theexternal casing 110 and cover the build material reservoir 112. Thebuild material reservoir 112 may be directly mountable within theexternal casing 110 or may be mountable within one or more intermediateinternal structures.

FIGS. 1D to 1F show certain aspects of a build material reservoiraccording to examples. For example, this may be the build materialreservoir 112 shown in FIGS. 1A to 1C.

FIG. 1D schematically shows a build material reservoir 104 according toan example. The build material reservoir 104 comprises an outerstructure 120, an outlet structure 121 and an internal aspirationchannel 122 coupled to the outlet structure 121. The outer structure 120may comprise a polymer box or bag of a predetermined thickness. In thelatter case, a bag may be shaped by molding and/or heat sealing, amongstother methods of manufacture. In the present example, the outletstructure 121 is arranged to be coupled to an aspiration system. Theaspiration system may form part of a supply system for athree-dimensional printing system, i.e. a system configured to supplythe three-dimensional printing system with build material. The outletstructure 121 may be formed as part of the outer structure 120 and/ormay be attached to the outer structure, e.g. via a coupling mechanismsuch as a threaded portion of the outer structure 120. The aspirationchannel 122 may comprise a rigid closed channel, such as a polymer tubethat is fixed to the outlet structure 121. The aspiration channel 122may end in an opening at a base of the outer structure 120. In thismanner, a low pressure such as a vacuum that is applied to the outletstructure 120 may cause a change in pressure in the aspiration channel122, i.e. a lowering of pressure. If the build material reservoir 104contains build material, the low pressure at the opening of theaspiration channel 122 may cause build material to be sucked up theaspiration channel 122 and to be extracted via the outlet structure 121.In one case, the aspiration channel 122 may be separate from the outletstructure 121. In this case, the outlet structure 121 may be connectableto the aspiration channel 122. In another case, the aspiration channel122 and the outlet structure 121 may form two parts of a commonstructure. The aspiration channel 122 aids the extraction of buildmaterial from the build material reservoir 104 in certain examples. Inother examples, e.g. where the outlet structure 121 is located at a baseof the build material reservoir 104, build material may be extractedfrom the outer structure 120 without the aspiration channel 122.

FIG. 1E schematically shows a build material reservoir 105 according toan example that is provided with a surround 125. The build materialreservoir 105 comprises components similar to build material reservoir104. In this example, the outer structure 120 may comprise a deformablestructure, such as a flexible polymer bag. The deformable structurecomprises at least one deformable side wall. A deformable structureassists in emptying the build material reservoir 104 by having the atleast one deformable side wall deform inwards (e.g. collapse) when thepressure inside the outer structure 120 is below a given value (e.g.when a vacuum is applied via outlet structure 121. The deformablestructure may also deform due to the presence of build material withinthe structure, e.g. the presence of build material may exert an outwardspressure that is applied to the side walls. An extent to which adeformable structure deforms outwards may be limited by the surroundand/or a tension in the deformable structure.

The surround 125 surrounds the outer structure 120. It may be formedfrom a material with a higher stiffness that the outer structure 120, inwhich case it may be used to support the outer structure 120. In onecase, the outer structure 120 may be physically attached, at leastpartially, to the surround 125, e.g. through a fastening substance suchas a glue or tape. The outer structure 120 may be supplied in a flat orfolded form attached to the surround 125, or may be inserted into thesurround 125. In FIG. 1E, the outer structure 125 ends in a vertex 123.The aspiration channel 122 may be positioned with its end at the vertex123. In three dimensions the vertex 123 may form the point of apolyhedral portion at a base of the outer structure 120, e.g. in theform of a cone or pyramid. The polyhedral portion may have a height thatis a proportion of the height of the outer structure 120, e.g. a thirdor a quarter of the height. The height of the polyhedral portion may bedetermined based on an angle of as described with reference to laterexamples. A shape of the outer structure 120 may be formed by heatsealing sides of the outer structure 120. In one example, a shape of adeformable outer structure 120 may be at least partially expanded, byinsertion of the aspiration channel 122 via the outlet structure 121 oranother opening (such as 113 in FIG. 1B), e.g. insertion of theaspiration structure may apply a force to a base of the deformablestructure and thereby help extend it to, or near, its fullest extent inthe direction of the insertion. In FIG. 1E, the surround 125 matches andsupports the vertex 123. Having a vertex located at the lowestoperational point of the structure 120 enables build material to beefficiently extracted from the build material reservoir 105, e.g. thebuild material is fed towards the vertex by gravity and thus collectsaround the vertex in the interior of the outer structure 120 where itmay be extracted using the aspiration channel 122. Additionally, atleast one deformable side of the outer structure 120 may also feed buildmaterial towards the vertex.

FIG. 1F is a schematic illustration of an example build materialreservoir 106 showing how the outer structure 120 may deform in use.Again, in implementations the shape of the outer structure 120 may varyfrom that shown in the Figure. In FIG. 1F, the outer structure 120 isfixed to the surround 125 in a number of locations 126. In one case, thesurround may be open at the top, e.g. the surround may have a number ofsides to surround the outer structure 120, plus base elements tosurround any flat or polyhedral lower portion. When a low pressure suchas a vacuum is applied at the outlet structure 121 this may lower thepressure within the outer structure 120, causing the outer structure todeform inwards as shown, apart from where it is constrained by anyfixation locations 126.

FIG. 1G is a schematic illustration of an example build materialcontainer 107 showing how a build material reservoir, show as 105 inFIG. 1E, may be mounted within the external casing 110 shown in FIGS. 1Aand 1C. In FIG. 1G a support structure 130 is provided that accommodatesthe vertex of the outer structure 120 of the build material reservoir.In certain cases, such as that of FIG. 1E, the support structure 130 mayaccommodate the vertex of the surround 125 around the outer structure120. Although a conical or pyramidal base is shown in FIG. 1G, thesupport structure 130 may accommodate other three-dimensional shapes. Incertain cases, the support structure 130 may be molded to fit aparticular three-dimensional shape of either the outer structure 120 orthe surround 125.

FIG. 1H shows a support structure 135 for a build material container108. The support structure 135 in this example comprises a polyhedralindentation, e.g. a valley or molded concavity, in an upper portion ofthe support structure 135. The polyhedral indentation is configured toreceive a base of the outer structure 120 for the build materialcontainer. A base of the support structure 135 is arranged to rest on aplanar surface, such as a base of the external casing 110. In certaincases, the support structure 135 may be dimensioned to be accommodatedwithin a base of a cuboid external casing 110. The support structure 135may be constructed from a molded material, such as polymer or naturalfiber (e.g. board or paper based). The latter material enables recyclingof the support structure 135 following use. FIG. 1I shows the supportstructure 135 from above and featuring an indentation or concavity 136.

FIGS. 2A and 2B show example three-dimensional printing systems that maybe used with the build material container examples of FIGS. 1A to 1I.

FIG. 2A shows a three-dimensional printing system 201 comprising athree-dimensional printer 205, a build material container 210, and abuild material transport system 215 for transporting build materialbetween the build material container 210 and the three-dimensionalprinter 205. The three-dimensional printing system 201 may be anadditive manufacturing system for generating three-dimensional objectsusing build material stored in the build material container 210. Thethree-dimensional printer 205 may comprise a three-dimensional printingpart and a separate build material management part. Alternatively, thethree-dimensional printer 205 may comprise a three-dimensional printingmodule and a build material management module incorporated within asingle apparatus. The transport system 215 may comprise an aspirationsystem (not shown), which generates a suction, or vacuum, pressure toextract build material from the build material container 210 fordelivery to the three-dimensional printer 205 by pneumatic transport.Connection between the transport system 215 and the build materialcontainer 210 is facilitated by a build material outlet structure 220.This may comprise the outlet structure 121 described with reference toFIGS. 1D to 1F. The build material container 210 may also provide anaspiration channel through which build material stored in the container210 may be extracted or “aspirated” via the transport system 215 to thethree-dimensional printer 205. According to some examples, the transportsystem 215 is provided with a nozzle structure (not shown) to connect tothe outlet structure 220 of the container 210 in a sealable manner (e.g.a gas/fluid seal), thereby facilitating pneumatic transport of the buildmaterial from the build material container 210 to the three-dimensionalprinter 205.

FIG. 2B shows one example of a three-dimensional printing system 202that comprises a three-dimensional printer 205 and a separate buildmaterial management station 230 (sometimes referred to as a “processingstation”). If the build material management station 230 is arranged tosupply the three-dimensional printer 205 with build material it may bereferred to as a “supply system”. In FIG. 2B, the build materialmanagement station 230 comprises the transport system 215 to extractbuild material from the build material container 210 via the outletstructure 220. In certain cases, the build material management station230 may be arranged, additionally or alternatively, to fill, or transferbuild material to, the build material container 210 via an inletstructure using the transport system 215. In FIG. 2B, a build unit 235such as a moveable trolley is filled with build material by the buildmaterial management station 230 and then is moved to thethree-dimensional printer 205 for the printing of an object. Forexample, the build unit 235 may be couplable to both the build materialmanagement station 230 and the three-dimensional printer 205. In otherexamples, the build unit 235 may be fixed and/or have a constrainedmovement path, e.g. comprise a moveable carriage. Although thethree-dimensional printing system 202 is shown as having separate unitsin FIG. 2B, in certain implementations these may form separate sectionsof a single apparatus. The build material management station 230 maymanage build material extracted from build material container 210 inorder to fill the build unit 235 with build material for use in asubsequent three-dimensional printing operation. In certain cases, thebuild unit 235 may be returnable to the build material managementstation 230 following printing. For example, the build materialmanagement station 230 may be used to remove non-solidified buildmaterial following completion of a printing operation. Non-solidifiedbuild material may be used as recycled build material for futureprinting, e.g. used to fill the build unit 235 for future objects to bebuilt. In one case, the build material management station 230 may mix“used” build material with “virgin” build material previously extractedfrom the build unit 235 in user-defined proportions. The build materialmanagement station 230 may comprise storage units to store both “used”and “virgin” build material.

FIGS. 3A to 3F schematically depict a set of structures 301-305 that maybe used, individually or in combination, to form a build materialcontainer according to certain examples. As will be made clear, aspectsof the structures 301-305 correspond to similar aspects of thestructures 101-109 described above in relation to FIGS. 1A to 1I. Unlessstated otherwise, in some examples such aspects have form and functionas described above.

FIG. 3A schematically shows a build material container 301 for athree-dimensional printing system. FIG. 3A is presented as a schematicvertical cross section from one side. The container 301 comprises anexternal casing 310 and a lower compartment 311 to receive a buildmaterial reservoir. As described above in relation to FIGS. 1A to 1I,the build material reservoir may, in some examples, comprise adeformable structure having an inlet and/or outlet, and an aspirationchannel within the deformable structure that is coupled to the outlet.

Similarly as described above in relation to FIG. 1A, the external casing310 may be any three-dimensional shape and may be constructed from avariety of materials including corrugated media or board, polymers andmolded natural fibers.

The container 301 comprises at least one load-bearing element 312. InFIG. 3A, the load-bearing element 312 is aligned with an axis of thelower compartment 311. In FIG. 3A, the element 312 is also shown aslocated centrally within the lower compartment 311 and aligned with thevertical axis thereof. In other examples, the element 312 may benon-central and/or have a non-vertical alignment. The axis may representa height dimension of the build material container, i.e. a dimensionwherein gravitational loads are applied. The container 301 comprises anupper compartment 313 below an upper surface 314 of the external casing310. The upper compartment 313 and the lower compartment 311 areseparated by a lower surface 315, the at least one columnar load-bearingelement 312 being arranged below the lower surface. Although a columnarload-bearing element is shown in FIG. 3A for ease of explanation, theload-bearing element 312 may be arranged to distribute a vertical loadfrom the lower surface 315 to a base of the build material containerusing a non-columnar structure, e.g. using arches and/or diagonalmembers. When using non-columnar structures, the at least oneload-bearing element 312 may not be aligned with the axis of the lowercompartment 311 to support loading on top of the build materialcontainer 301.

In some examples, the upper and lower surfaces are formed from the samematerial as the external casing 310. For example, the upper and/or lowersurfaces may be formed from one or more flaps of the external casing310. Alternatively, the upper and/or lower surfaces may be formed by apiece or pieces of material separate from the external casing 310. Forexample, the lower surface may comprise a partition as described withreference to FIGS. 9A to 9F below.

In other examples, the upper and/or lower surfaces are formed from adifferent material from the external casing 310. In one such example,the external casing 310 is formed from corrugated cardboard and theupper and/or lower surfaces are formed from a polymer.

The upper compartment 313 comprises stiffening members 313 a, b arrangedto distribute load received from the upper surface 314 to the at leastone load-bearing element 312. The stiffening members 313 a, b arearranged around an aperture 316 for a channel structure of the buildmaterial reservoir. The stiffening members 313 a, b distribute this loadto the at least one load-bearing element 312. The stiffening members arestiffening in that they strengthen the ability of the build container towithstand vertical loads, e.g. they stiffen the upper compartment 313.

As such, a load applied to the top of the container 301 is transferredthrough the upper compartment 313 to the load-bearing element 312, andthereby is not applied to the channel structure or, more generally, thereservoir. This allows loads to be applied to the top of the container301, for example by stacking additional build material containers, orother items, on top of the container 301, without damaging the channelstructure or compacting build material in the reservoir. Load is thusdistributed through the container 301 without affecting the buildmaterial therein. The simplicity of storing and transporting containers301 is thus improved.

The transfer of force through the load-bearing element 312 also causesthe force that is transferred through the walls of the external casing310 to be reduced. The external casing thus has more flexibility withregard to materials and design, allowing, for example, lighter, lessstiff, and generally cheaper materials to be used for the casing 310without compromising the integrity of the container 301 or causing it tobuckle.

FIG. 3B shows schematically a build material container 302 according toa further example. In FIGS. 3B, 3E and 3F, upper surface 314 is omittedfor clarity. Upper surface 314 may be formed from flaps of the externalcasing 310 that are folded over prior to transport. The container 302comprises an external casing 310 and a lower compartment 311 asdescribed above in relation to FIG. 3A. The container 302 furthercomprises a plurality of load-bearing elements 312 a, 312 b arrangedaround the exterior of the lower compartment 311, e.g. within theexternal casing 310. FIG. 3B shows separate parts 313 a, 313 b of anupper compartment 313, with one part corresponding to each load-bearingelement 312 a, 312 b. These separate parts 313 a, b comprise theaforementioned stiffening members. Increasing the number of load-bearingelements in this manner allows a load applied to the top of thecontainer 302 to be spread more evenly, improving the strength of thecontainer 302.

FIGS. 3C and 3D shows schematically a build material container 303according to a further example. The container 303 comprises an externalcasing 310 as described above in relation to FIG. 3A. The containerfurther comprises a plurality of build material reservoirs 320 a, b forholding build material, for example as described above in relation toFIGS. 1B to 1F or the later Figures. The container 303 comprises aplurality of load-bearing elements 312 a-c arranged around the buildmaterial reservoirs 320 a, b. Parts 313 a-c of an upper compartment actas stiffening members and each correspond to a load-bearing element 312a-c, such that load applied to the top of the container 310 istransferred via parts 313 a-c of the upper compartment to thecorresponding load-bearing elements 312 a-c. The load is thus spreadacross the load-bearing elements 312 a-c. FIG. 3C shows a front crosssection with a front side wall removed. FIG. 3D shows a lateral crosssection at a center of the container. In FIG. 3C the location of buildmaterial reservoirs 320 a, b and central load-bearing element 312 bbehind load-bearing elements 312 a, c are shown using dashes. In FIG. 3Dthe load-bearing elements 312 a, c are not shown. In FIG. 3D, at leastone load-bearing element 312 b is located between the build materialreservoirs. This improves the strength of the container 303 relative toa similar container in which the load-bearing elements are arrangedaround the edges of the container. Such an arrangement may aidcompliance with drop safety tests.

For clarity, a support structure such as that shown in FIGS. 1G to 1H isnot shown in FIGS. 3A to 3D. When such a support structure is supplied,the load-bearing members may be located within apertures in the supportstructure and/or positioned around the support structure.

In one example implementation, an external casing 310 may be 1.5 m tall(i.e. a length in a z dimension as indicated in the Figures), with alength of 1 m (i.e. a length in an x dimension as indicated in theFigures) and a width of 0.75 m (i.e. a length in a y dimension asindicated in the Figures). A height of examples may generally be withina range of 1 to 2 m and widths and lengths may be selected from a rangeof 0.5 to 2 m. A width and length of the external casing 310, e.g.dimensions of a horizontal cross section, may have equal or differentvalues. A height of the upper compartment 313 (e.g. a z-dimension value)may be between 5 to 20 cm and may depend on a height of an outletstructure of a build material reservoir. As such, in these cases,load-bearing elements may have a height of between 130 to 145 cm.Stiffening members 313 a, b may have a length up to or equal to a widthof the external casing 310, e.g. 75 cm. A length of stiffening members313 a, b may be less than the length of the side of external casing.Stiffening members 313 a, b may have a cross-sectional height that isapproximately equal to a height of the upper compartment 313, e.g.between 5 to 20 cm. Stiffening members may have a cross-sectional widththat is between 5 to 20 cm, where in one case the stiffening members maycomprise a cuboid with x, y and z dimensions of 10×75×6 cm. Ifcorrugated media is used, the external casing, stiffening members,load-bearing elements and/or surfaces may have a thickness of between 2to 10 mm. A lower support structure may have a height of around 30 to 50cm. A lower polyhedral of a build material container may have a heightof around 20 to 40 cm.

A filled build material container of the above dimensions may weighapproximately 150 to 180 kg including a weight of the build materialcontainer. An unfilled build material container may weigh between 20 to30 kg. The reservoirs of an example unfilled build material containerhave a total internal volume of around 0.75 m³. If build materialcontainers of this size are stacked, a maximum load may compriseapproximately 1500 to 1800 Newtons.

It should be understood that the dimensions and loading set out aboveare for one example, and may vary according to differentimplementations.

FIG. 3E shows schematically a plan view of a build material container304 according to an example, e.g. a horizontal cross section below thelower compartment. The container 304 may be configured in the samefashion as the container 303 described above in relation to FIGS. 3C and3D. For clarity, the upper compartment is not shown. The container 304comprises a plurality of individual build material reservoirs 325,arranged in a two-by-two grid formation. The container 304 furthercomprises load-bearing elements 326, with one such element positioned ateach intersection of the two-by-two grid. This allows loads to be spreadeffectively across the load-bearing elements. The load-bearing elements326 in this example are columnar.

The load-bearing elements have cross-sectional shapes corresponding totheir positions within the grid, such that elements at the outer cornershave a right-angled “L” shape, elements in the middle of the outer sideshave a “T” shape, and the element in the middle of the grid has a “+”shape. In other examples different shaped elements may be used, and, forexample, each element may have the same shape. This helps make efficientuse of the internal volume available to accommodate the reservoirs 325whilst not compromising the load bearing capability of the elements. Inone case, the load-bearing elements are formed from a material similarto the external casing 310, e.g. a type of corrugated media that isfolded and/or affixed into the shapes shown. In another case, theload-bearing elements are formed of a different material, e.g. one witha higher load strength such as metal or polymer. In other examples, theload-bearing elements have other cross-sectional shapes, for examplecircular or rectangular cross sections.

FIG. 3F shows schematically a plan view of a build material container305 according to an example. The build material container may generallybe configured as described above in relation to FIGS. 3A to 3D. Thecontainer 305 comprises build material reservoirs 325 and load-bearingelements 326, configured as described above in relation to FIG. 3D. Thecontainer 305 comprises an upper compartment 330. The upper compartment330 has an “H” shape and is positioned above a plurality of theload-bearing elements 326. Dotted lines indicate where load-bearingelements 326 lie directly below a part of the upper compartment 330.

In FIG. 3E, the upper compartment 330 comprises two opposing stiffeningmembers 327 a, b that extend along widths of the upper surface, e.g.along a width or other horizontal dimension of the casing 310. The uppercompartment 330 further comprises a stiffening member 328 that extendsalong a length of the upper surface. This represents an exampleconfiguration: in other examples, the upper compartment 330 comprisesone or two of these stiffening members 327 a, b, 328. In yet furtherexamples, the upper compartment 330 comprises additional stiffeningmembers.

The stiffening members 327 a, b are, in some examples, folded stiffeningmembers. In one such example, the stiffening members 327 a, b are formedfrom folded flaps of the external casing of the container 305. As such,in certain cases, the stiffening members may be constructed fromcorrugated media. One or more perpendicular stiffening members 328 maythen extend across the upper compartment 330 between the stiffeningmembers 327 a, b. As shown in FIG. 3E, load-bearing elements of thecontainer 305 are arranged to receive a load from the stiffening members327 a, b, 328. The stiffening member 328 may be constructed by foldingan end of a flap of the external casing inward towards the interior ofthe container 305. The height of the stiffening members 327, 328 may beconfigured to be a height of the upper compartment 330. Exampledimensions are provided above.

FIG. 3G shows an example kit 340 for constructing a build materialcontainer for a three-dimensional printing system, for example asdescribed above in relation to FIGS. 3A to 3E. The kit comprises anouter box 310 having a height, a length and a width. For example, theheight may be a vertical (z) dimension and the length and width may behorizontal dimensions (x, y). In one case, the box may be 1×0.75×1.5 min x, y and z dimensions. The outer box may be supplied as a net orblank to be folded and assembled, or may be supplied ready formed, e.g.as a molded polymer box. The box may have dimension ranges as discussedabove.

The kit 340 also comprises an internal carton 345 for storing buildmaterial for the three-dimensional printing system, the internal carton345 to fit within the outer box 310 and having a height less than theheight of the outer box 310. The carton 345 may thus form a reservoir320 for build material, as described above. The internal carton 345 maycomprise a surround and a deformable structure as described withreference to other examples herein. The deformable structure maycomprise a polymer bag that is affixed in place within the surround.

The kit comprises a planar portion 346 for fitting within the outer box310, e.g. parallel to the base of the box 310, above the internal carton345.

The kit 340 comprises a plurality of elongate load-bearing members 312having a length equal to or greater than that of the internal carton 345and less than the height of the outer box 310. These members 312 areconfigured to fit, in use, around the internal carton 345 within theouter box 310. In some examples, additional stiffening members are alsoprovided as part of the kit 340. These stiffening members are arrangedto fit, in use, between a surface of the outer box 310 and the planarportion 346. The stiffening members can thus be configured to distributea load from the surface to the planar portion 346. The planar portion346 is thus configured to, in use, receive a load from the outer box 310and to distribute said load to the elongate load-bearing members 312.

In some examples, the stiffening members comprise portions of the outerbox 310. For example, the stiffening members may comprise foldedportions of the outer box 310. In other examples, stiffening members maybe separate members, such as a metal or polymer reinforcement memberattached to a cardboard outer box 310.

From the kit may thus be assembled a build material container such asthat described above in relation to FIGS. 3A to 3E.

In one case, there is provided a plurality of build material containersas described in examples, wherein the build material containers containbuild material and are stacked vertically, i.e. in the z dimension.

FIGS. 4A and 4B show methods 401,402 according to examples. FIG. 4Ashows a flow diagram of a method 401, according to examples, for makinga build material container for a three-dimensional printing system asdescribed in more detail above. The method may be performed with a kitas described in the preceding paragraphs.

The method 401 comprises a block 404 of providing an external casing forthe build material container. This may be the outer box of the kit. Themethod 401 then comprises a block 405 of arranging the build materialreservoir within the external casing. This may comprise slotting asurround of the build material reservoir into an interior of theexternal casing or assembling the external casing around the buildmaterial reservoir. The method may comprise inserting an aspiration tubeinto the reservoir. At block 406, the method 401 comprises arranging atleast one load-bearing element around the build material reservoir. Thismay comprise slotting the load-bearing elements into the interior of theexternal casing from an open top of the external casing. This maycomprise, amongst others, one or more of: arranging load-bearingelements in the corners of the external casing, arranging one or morecentral load-bearing elements, and arranging load-bearing elements atthe side of the external casing. Load-bearing elements may be arrangedas per FIG. 3E such that each build material reservoir is surrounded byat least four load-bearing elements. At block 407, the method 401comprises arranging a partition above the build material reservoir. Thepartition comprises an aperture of a channel structure of the buildmaterial reservoir, and is supported upon the at least one columnarload-bearing element. This may comprise placing the partition on top ofany build material reservoirs and load-bearing elements, ensuring thatthe channel structures are fed through the apertures within thepartition.

In some examples, the method further comprises supplying build materialto the channel structure to fill the build material reservoir.Performing such supplying increases pressures within the container, andthus may be performed after arranging the load-bearing elements aroundthe reservoir to avoid difficulty in inserting the load-bearingelements.

In certain cases, the method 401 may comprise a further block ofarranging a set of stiffening members upon the partition around thechannel structure, and closing the external casing. Such stiffeningmembers are configured to transfer loads, applied to the top of thecontainer, to the load-bearing elements. The method 401 may compriseconstructing the stiffening members from upper sections of the externalcasing, e.g. by folding the upper sections. In other examples, thestiffening members may be supplied for fastening to the partition and/orinternal side walls of the external casing.

FIG. 4B shows a flow diagram of a method 402, according to a particularexample, for constructing a build material container. In examples, thebuild material container is as described above.

The method 402 comprises a block 410 of forming a two-dimensional net orblank of the build material container. A net or blank is a flattenedform of the three-dimensional build material container that make beassembled into shape. For example, this may be formed, for example, bycutting a sheet of corrugated media and pre-scoring portions thereof tofacilitate folding. The two-dimensional net or blank comprises at leastone base portion and side portions having foldable upper sections,wherein a base portion is a portion useable to construct a base of thethree-dimensional build material container and a side portion is aportion useable to construct a side of the three-dimensional buildmaterial container.

FIG. 5 shows a schematic representation of such a net or blank 500. Thenet 500 comprises base portions 501 and side portions 502. Two of theside portions have foldable upper sections 503. The base portions 501may be folded over each other to create a base of the external casing.In other examples, the base portions may comprise a single planarportion foldably coupled to one of the side portions 502. Variousconfigurations are possible in practice.

Returning to FIG. 4B, the method 402 comprises a block 411 of foldingthe side portions to generate a three-dimensional form of the buildmaterial container. This block may also involve fixing or fastening theside portions and/or base portions into place, e.g. using glue or tape.At block 412, the method 402 comprises configuring side stiffeningmembers that extend at least along a length of the side portions. Inthis example, this comprises folding a first set of opposing uppersections to generate upper stiffening members that extend along oppositesides of the build material container. For example, this may comprisefolding a flap into a cuboid member that is foldably coupled to the sideportion and has a height corresponding to the upper compartment. Thismay be performed for two opposing side portions 502. The method 402 thencomprises a block 413 of folding a second set of opposing upper sectionsover the stiffening members to form an upper surface of the buildmaterial container. The upper stiffening members are thereby arranged todistribute a load received on the upper surface to the side stiffeningmembers, as described above.

The upper sections may comprise flaps of the two-dimensional net orblank. The upper stiffening members may accordingly comprise cuboidmembers formed from folding opposing flaps in a plurality of locations.An additional set of stiffening members may also be generated by foldingthe ends of the other two opposing flaps, i.e. those that form the uppersurface. In this case, the flaps may be longer than half the width orlength of the upper surface, i.e. half the width or length of the uppersurface plus a height of the upper compartment. As such an edge of theadditional set of stiffening members may contact the partition totransfer a load to the partition.

In some examples, the method 402 comprises mounting at least one polymerbag for holding build material within the side portions, wherein theload bearing members act as a guide to locate the polymer bag within theside portions. In other cases, the load bearing members may be insertedafter the polymer bags, e.g. to further guide and support the bagswithin the interior of the external casing. In this example, the polymerbags may be mounted within a surround as described with reference toother examples. For example, this is shown in FIG. 16.

In some such examples, the method 402 comprises installing a planarpartition between the polymer bag and the upper surface, the planarpartition comprising at least one aperture to support at least onechannel structure of the polymer bag.

Certain examples described with reference to FIGS. 3A to 3E, and FIGS.4A and 4B, add a set of lead-bearing members within a build materialcontainer to strengthen the container, e.g. to support the stacking ofcontainers. It enables bearing a load on an upper surface of thecontainer in a manner than does not damage channel structures of thebuild material reservoirs, or compact the build material in thereservoirs. For example, a fully-loaded build material container incertain implementations may weigh up to 180 KG. A combination ofvertical load bearing members may be used within the container togetherwith horizontally-aligned upper stiffening members. The latter membersdistribute a load on an upper surface of the container around thechannel structures of the build material reservoirs and through the loadbearing members.

FIGS. 6A to 6I introduce a set of structures that may be used,individually or in combination with each other and/or with the relatedstructures described above, to form a build material container. Thesestructures help to protect channel structures of a build materialcontainer, e.g. during transport, and may be used to indicate use ofbuild material within the container. The structures may be configured tofacilitate access to build material reservoirs within the build materialcontainer while reducing or avoiding tearing or ripping of an externalsurface of the container.

FIG. 6A shows schematically a build material container 601 for athree-dimensional printing system, according to an example. Thecontainer 601 comprises an external casing 610 having an outer surface.The external casing may for example be configured as described inrelation to other examples.

The container 601 comprises an internal reservoir 611 for holding buildmaterial, the internal reservoir being positioned within the externalcasing. The internal reservoir 611 comprises an outlet structure 612 forcoupling to an element of a three-dimensional printing system. In FIG.6A, the outlet structure 612 is positioned below the outer surface ofthe casing 610, wherein the outer surface is an upper surface of thecasing 610. In other examples, the outer surface may comprise a sidesurface and the outlet structures may be orientated to face this sidesurface.

The external casing 610 comprises a structurally weakened portion 613arranged within an interior of the outer surface above the outletstructure. The structural weakening may, for example, be by way ofperforations in the external casing, partial cutting of the externalcasing and/or thinning of the external casing. In examples, thestructurally weakened portion 613 is pivotable about one side within theouter surface to remove the structurally weakened portion 613 from theexternal casing 610, such that the pivoting enables the user to removethe structurally weakened portion 613 for example by tearingperforations joining the portion 613 to the remainder of the externalcasing 610 (i.e. by tearing the side of the portion about which theportion pivots).

Responsive to a force applied to the structurally weakened portion 613,the structurally weakened portion 613 is separable to create an aperturein the outer surface, wherein the aperture enables access to the outletstructure 612. As such, the outlet structure 612 is covered until thestructurally weakened portion 613 is separated. A consequence of this isthat the outlet structure 612 can be protected from damage andenvironmental contamination during transport and storage, and exposedwhen ready for use.

FIG. 6B shows a perspective view of a build material container 602,which is configured as described above in relation to FIG. 6A. Thestructurally weakened portion 613 is shown with a dashed line toindicate the weakening, and the outlet structure 612 is shown with adash-dot line to indicate that it is covered by the structurallyweakened portion 613.

The position of the structurally weakened portion 613, within aninterior of the outer surface, is evident in FIG. 6B. This allowsseparation of the portion 613 without compromising the structuralintegrity of the top or side walls of the container 602, or causing themto buckle. This mitigates weakening of the container 602, in particularwhen stacked with similar containers in storage or transit. For example,when the structurally weakened portion is used together with theexamples of FIGS. 3A to 3E, the structurally weakened portion may bearranged such that it does not overlap or interfere with the stiffeningmembers 327 and/or 328. As such load is borne by the stiffening membersunderneath the upper surface rather than upon the structurally weakenedportions. Although one structurally weakened portion is shown in FIGS.6A and 6B, there may be a plurality of portions, e.g. when used incombination with the examples of FIGS. 15A, 15B and 16.

FIGS. 6C to 6E schematically show example structurally weakened portions603-605. Each such portion 603-605 comprises an aperture 615 that isformed within the outer surface of the container to aid application offorce to an underside of the respective structurally weakened portion.This aperture may have a variety of shapes, including being elongate asshown in the Figures. For example, the apertures may be configured suchthat a user may insert their fingers into the aperture and thereby pullon the underside of the structurally weakened portion, to separate itfrom the external casing of the container. In other examples theaperture may be omitted.

In certain examples, the aperture 615 forms at least part of one side ofthe structurally weakened portion and the structurally weakened portionfurther comprises at least three structurally weakened sides, whereineach structurally weakened side comprises cut portions interspersed withscored portions. For example, the weakening may be by way ofperforations, whereby to assist the user in removing a given portionwith ease and without tearing the surrounding portions of the externalcasing. In FIGS. 60 to 6E, dashed lines indicate perforations, anddash-dot lines indicate the position of the outlet structure 612 beneaththe respective structurally weakened portions 603-605.

Referring to FIG. 6C, the perforations 616 of the portion 603 are evenlyspaced around the perimeter of the portion 603.

In some examples, the cut portions of two lateral structurally weakenedperforated sides of the structurally weakened perforated portion vary inat least one of length and spacing, such that an amount of force toseparate the lateral structurally weakened perforated sides increaseswith distance from the elongate aperture. FIG. 6D shows schematically anexample of such a portion 604. Near the aperture 615, the perforations617 are closely spaced. This reduces the force required to tear thissection such that the perforations may be torn by a user withoutdifficulty.

Further from the aperture 615, the perforations 618 are widely spaced.The force to tear this section is high such that a user may typicallyhave difficulty tearing this section alone, but the weakening of thecontainer is correspondingly less. This may improve protection duringstorage and transport, e.g. prevent the structurally-weakened portionfrom being accidentally separated during storage and transport. As such,when removing the weakened portion 604, the user first tears the closeperforations 617 with ease. The momentum generated in tearing thisportion provides for easy tearing of the wide perforations 618. The usermay thus tear the perforations 617, 618 with ease, whilst reducing theweakening of the container. Moreover, following separation of theperforations 617, it may be easier for a user to apply a larger force,as the structurally weakened portion may be pivoted about the sideopposite the aperture 615. Although the perforations 617, 618 are shownas discrete sections for ease of explanation, it should be understoodthat in practice there may be a continuous or graduated change in alevel and type of structural weakening along the sides.

FIG. 6E shows schematically a further example of a structurally weakenedportion 605. The at least three structurally weakened sides of thestructurally weakened portion 605 are joined by rounded corners 620 a,b. The portion 605 further comprises closely spaced perforations 617 andwidely spaced perforations 618. In some examples, in addition tocomprising rounded corners 620 a, b, the portion 605 comprises evenlyspaced perforations, similarly as shown in FIG. 6C, as opposed tocomprising differently-spaced perforations.

FIG. 6F shows schematically such a rounded corner 620. A central portion621 of the rounded corner is uncut to enable a hinge effect when theforce is applied. This hinge effect applies a torsion to thestructurally weakened side between the rounded corners: as the part 622of the portion 605 nearer to the elongate aperture 615 is pulled towardsthe user, the side 623 between the rounded corners is pushed away fromthe user. This torsion aids in tearing the side 623 between the roundedcorners.

FIG. 6G shows schematically a further example of a structurally weakenedportion 606. The dark lines represent cuts that are made in the externalcasing, whereas blank sections between the dark lines represent areaswhere the structurally weakened portion 606 is joined to the externalcasing. The portion 606 comprises an aperture 615 as described in moredetail above. The structural weakening is by way of a microperforationsystem. A structurally weakened side 625 opposite the elongate aperturecomprises longer cut portions than the two lateral structurally weakenedsides 626 a, b to prevent tearing of the external casing 610. Forexample, sides 626 a, b may comprise a series of cuts having a firstlength, and side 625 may have a series of cuts having a second length,wherein the second length is greater than the first length. As thelength of the cuts is longer on side 625 there are fewer sections of theportion 606 that are joined to the external casing 610. This reduces alikelihood of tearing as force is concentrated on the (shorter) joinedsections. This aids the user in cleanly removing the portion 615 fromthe external casing 610 without causing damage. This feature may, asshown in FIG. 6G, be implemented in combination with rounded corners 620a, b as described in more detail above in relation to FIGS. 6E and 6F.Alternatively or additionally, this feature can be used in combinationwith varying perforation spacing, as described above in relation to FIG.6D.

FIG. 6H shows schematically a top-down view of a build materialcontainer 608, according to examples of the present disclosure. Thecontainer 608 comprises a plurality of internal reservoirs each forholding build material, each internal reservoir having an outletstructure in the form of an outlet nozzle 630 a-c (depicted withdash-dot lines to indicate their position beneath the external casing610). The container 608 further comprises a plurality of structurallyweakened portions 631 a-c spaced within the external casing 610, alignedwith each of the outlet nozzles 630 a-c. In some examples, otherconfigurations of structurally weakened portions 631 are used. Forexample, the container 608 may comprise four structurally weakenedportions 631, in a two-by-two-grid layout. Alternatively, thestructurally weakened portions 631 may be located in a side or a base ofa build material container. In some examples, the container 508comprises a partition within which the outlet nozzles are mounted, thepartition separating the internal reservoirs from the outer surface ofthe external casing as described in more detail below in relation toFIGS. 9A to 9F.

FIG. 6I shows schematically an example top-down in-use view of the buildmaterial container 608. The first structurally weakened portion 631 ahas been removed, with the nozzle 630 a exposed underneath. Thecorresponding reservoir has been fully used, and the nozzle 630 adisconnected from an element of the three-dimensional printing system.The absence of the first structurally weakened portion 631 a provides avisible indication that this reservoir has been exhausted. The nozzle630 a may be self-sealing or otherwise sealable, to prevent exit of anyresidual build material in the reservoir.

In FIG. 6I, the second structurally weakened portion 631 b has also beenremoved, and the nozzle 630 b is connected to a supply apparatus 632,for example a hose, of an element of the three-dimensional printingsystem. The corresponding reservoir thus provides build material to thethree-dimensional printing system.

In FIG. 6I, the third structurally weakened portion 631 c has not beenremoved, and the corresponding nozzle 630 c is concealed and therebyprotected from damage and from environmental contamination. The presenceof the third structurally weakened portion 631 c also provides a visibleindication that the corresponding reservoir is unused.

When the second reservoir is exhausted, the user may be alerted forexample by a pop-up warning on a terminal associated with thethree-dimensional printing system. The user can then remove the thirdstructurally weakened portion 631 c to expose the nozzle 630 c of thethird reservoir. Finally, the user can disconnect the supply apparatus632 from the second nozzle 630 b, and connect it to the third nozzle 630c. As noted above, the nozzles may be sealable, such that residual buildmaterial does not leak from the second nozzle 630 b followingdisconnection. The third reservoir is thus configured to supply buildmaterial to the three-dimensional printing system. When the thirdreservoir is empty, the user can disconnect the third nozzle 630 c,remove the container 608 and connect a first nozzle of a freshcontainer. In certain cases, more than one hose may be provided to allowmultiple ones of the outlets of the build material reservoirs to beconnected at any one time.

FIG. 7 shows schematically a net or blank 701 to construct a buildmaterial container. The blank may comprise corrugated media. The blank701 comprises sections 702-704 to form at least a base and sides of thebuild material container. The sections 702-704 comprise a plurality ofstructurally weakened portions 705, said portions 705 being at leastpartially separable from the build material container to access, whenassembled, an interior of the build material container.

In some examples, the plurality of structurally weakened portions 703are arranged in flaps 703 of the blank that form an upper surface of thebuild material container, as shown in FIG. 7. The flaps 703 may comprisetwo flaps 703 that are foldably coupled to respective side sections 704of the blank. The flaps may be longer than half a length or width of theupper surface to accommodate stiffening portions as described with inthe examples above.

In examples, the structurally weakened portions 705 comprise an apertureand a plurality of structurally weakened sides. As described in moredetail above, the sides may be variably weakened to reduce tearing ofthe blank during removal.

FIGS. 8A to 8B present methods 801-802 according to examples of thepresent disclosure.

FIG. 8A is a flow chart showing a method 801 of manufacturing a buildmaterial container for a three-dimensional printing system, the buildmaterial container being for example as described in more detail above.

The method comprises a block 805 of assembling a blank of the buildmaterial container, the blank comprising base and side portions. Theblank is configured such that folding the side portions generates athree-dimensional form of the build material container. The buildcontainer may be formed from corrugated media.

The method then comprises a block 806 of forming an upper surface of thebuild material container, the upper surface comprisingstructurally-weakened portions in upper sections of at least two sideportions. The structurally-weakened portions are aligned to generateapertures within the upper surface when at least three sides of thestructurally-weakened portions are separated from the upper surface.

In some examples, the method comprises providing a support structureabove the base and arranging multiple internal reservoirs within thesupport structure, each reservoir having an outlet structure for theextraction of build material. The method may then comprise arranging apartition above the multiple internal reservoirs, the partitioncomprising apertures for the outlet structure of said reservoirs,wherein separation of the perforated portions allows access to an uppercompartment formed between the partition and the upper surface. Thefunction of such a partition is described in more detail below inconjunction with FIGS. 9A to 9F.

FIG. 8B is a flow chart showing a method 802 of opening a build materialcontainer for a three-dimensional printer. The build material containermay for example be configured as described in more detail above.

The method 802 first comprises a block 810 of providing a build materialcontainer comprising an internal reservoir within a housing. At block811, the method 802 comprises applying a force to a structurallyweakened portion of the build material container, e.g. which has beenperforated or weakened by pre-cutting, by way of a first aperture in thehousing. At block 812, the method 802 comprises separating theperforated portion from the housing along lateral perforations,including pivoting the perforated portion about a base of the perforatedportion located opposite the first aperture. At block 813 a furtherforce is applied to separate the base of the perforated portion from thehousing. Removal of the perforated portion generates a second, largeraperture in the housing to allow access to an outlet structure of theinternal reservoir.

The method 802 may comprise, for example after performing theabove-described blocks, attaching a build material supply system to theoutlet structure to enable transfer of build material within theinternal reservoir to the three-dimensional printer. In some examples,the method 802 comprises, responsive to the internal reservoir beingdepleted, applying a force to a further perforated portion of the buildmaterial container to generate a further aperture in the housing. Themethod 802 may then comprise removing the further perforated portion toaccess a further outlet structure of a further internal reservoir of thebuild material container, and attaching the build material supply systemto the further outlet structure to enable transfer of build materialfrom within the further internal reservoir to the three-dimensionalprinter.

Certain examples described with reference to FIGS. 6A to 6I, FIG. 7 andFIGS. 8A and 8B, relate to enabling access to an internal reservoir of abuild material container. Certain examples keep outlet structures of thebuild material container protected during transit. This is achievedusing structurally weakened portions such as perforated windows in anupper surface of an external casing. Certain examples are directed toremoving the portions in a manner that reduces tearing. For example, byusing a particular perforation pattern and a hinging effect, whichpivots the window about its base before the last side is removed, theportion may be easily removed with minimal tearing.

FIGS. 9A to 9F are schematic diagrams showing certain examples of apartition that may be used with a build material container. Although notshown for reasons of clarity, the examples of a build material containershown in these Figures may have any of the features of the otherrelevant Figures. The examples described with reference to these Figuresmay aid the protection of build material reservoirs and prevent buildmaterial accumulating within the container.

FIG. 9A shows a build material container 901 that comprises an externalcasing 910. This build material container 901 comprises an internalcompartment 911 that is formed within the external casing 910. In FIG.9A the internal compartment 911 contains a build material reservoir 920.In certain examples, the build material reservoir 920 comprises adeformable structure to store build material; in other examples, thereservoir 920 has a fixed structure. The reservoir 920 has a channelstructure 913. The channel structure 913 may comprise one or more of anoutlet structure and an inlet structure. These structures mayrespectively provide an outlet for build material to be supplied fromthe build material reservoir 920 and an inlet for the supply of at leastone of build material or a gas such as air to the build materialreservoir. In these cases, the channel structure 913 may compriseseparate structures coupled to the reservoir 920 or a single,multi-function channel. FIG. 9A also shows a surround 925 that enclosesthe reservoir 920. This may comprise a box or other encasing polyhedron,or other shape, that supports and/or protects the reservoir 920. Thesurround 925 may also aid the assembly of the build material container901 by facilitating the insertion of the build material reservoir 920.The surround 925 may comprise a corrugated media or polymer packaging.

The build material container 901 of FIG. 9A also comprises a partition914 within which the channel structure 913 is mounted. For example, thepartition 914 may comprise a planar structure that has an aperture toaccommodate the channel structure 913. If there are multiple channelstructures 913, the partition 914 may comprise multiple apertures. Thepartition 914 may be formed from the same material as the externalcasing 910, a similar material or a different material. The partition914 may be recyclable. The partition 914 may comprise a sheet ofcorrugated media. The partition 914 is separate from the external casing910 and the surround 925, e.g. may comprise an independent sheet orelement that is not connected to the external casing 910 or the surround925 before it is put in place. In one example, the partition 914 doesnot form a foldably coupled portion of a blank for the surround or theexternal casing. When positioned in place as shown in FIG. 9A, thepartition 914 forms an upper surface of the internal compartment 911. Assuch the partition 914 restricts access to the internal compartment 911.Items that are dropped onto the partition 914 do not fall into theinternal compartment 911. Similarly, build material that is spilled ontothe partition 914 is collected rather than falling into the internalcompartment 911. In one case, the aperture for mounting the channelstructure 913 may provide a tight fit and/or the channel structure 913may comprise a lip or flange that extends over the edge of the aperture.For example, the channel structure 913 may comprise an outlet structurethat has a neck that has a smaller diameter than a head portion mountedabove the neck. The head portion in this case may be couplable to a hoseof a build material transport system, e.g. via mechanical and/ormagnetic mechanisms.

As shown in FIG. 9B, the partition 914 may comprise a planar portion anda plurality of side portions 915 that project upwards. These sideportions 915 form a raised edge or lip to the partition 914, such thatit acts as a tray. The side portions 915 may project upwards towards atop of the external casing 910, having a height that is at least aproportion of the distance from the partition 914 to the top of theexternal casing 910. The top of the external casing 910 may be a top ofthe external casing 910 after an upper surface of the external casing910 has been formed, e.g. by folding flaps of the casing over thepartition 914. In FIG. 9B, the side portions 915 abut side walls 916 ofthe external casing 910. For example, this may comprise making contactwith the side walls 916 so as to form a tight or snug fit against theside walls 916. When in place the partition 914 comprises a lowersurface of an upper compartment 918 of the external casing 910, and anupper surface of internal or lower compartment 911. The partition 914may be referred to as “cover reverse”, as it provide a reverse oropposite surface to the upper outer surface.

FIG. 9C shows an example where the external casing 910 accommodates aplurality of build material reservoirs 912. Two build materialreservoirs 912 a, 912 b are shown in the schematic cross-section of FIG.9C, however, any number of build material reservoirs 912 may beaccommodated, e.g. as described in more detail with reference to thelater Figures. For example, in certain cases, four or six build materialreservoirs may be mounted within the build material container 903.Although not shown for clarity, the build material reservoirs 912 a, 912b may be as shown in FIG. 9A, or any of the other Figures such as FIGS.1D to 1F. Additionally, each build material reservoir 912 a, 912 b maybe mounted within a support structure, as for example shown in FIG. 1Gto 1I. In FIG. 9C, the partition 914 has a plurality of apertures forthe respective channel structures of the build material reservoirs 912.These may comprise apertures for an outlet and an inlet per buildmaterial reservoir 912. The partition 914 in this case may also comprisethe side portions shown in FIG. 9B.

FIGS. 9D to 9F show schematically how an example partition 914 may beheld in place within a build material container 904.

FIG. 9D shows a schematic isometric view of a partition 914 having aplanar portion 914 and side portions 915, e.g. forming a tray-likeindependent structure that may be placed on top of the build materialreservoir, e.g. including the surround, within an external casing 910.FIG. 9D also shows an example outlet aperture 918 and inlet aperture 919for a case where one build material reservoir is provided that has bothan outlet structure and an inlet structure.

FIG. 9E shows an example of the build material container 904 where theside portions 915 of the partition 914 are accommodated between sidewalls 916 of the external casing 910 and stiffening members 923 arrangedabove the partition 914. The stiffening members 923 in FIG. 9E arecuboid members that help to distribute a force applied to an uppersurface (not shown) of the external casing 910 through the planarportion of the partition 914 to load bearing elements 924 that extendfrom the lower surface of the partition 914 to a base of the externalcasing 910. As described elsewhere, e.g. in relation to FIGS. 3A to 3F,stiffening members 923 and load bearing elements 924 may be implementedin a number of different ways while maintaining equivalent functionalaspects. In the example of FIG. 9E, the stiffening members 923 areconstructed from folding respective upper flaps of two sides of theexternal casing 910. For example, rather than folding the flaps to formpart of an upper surface of the external casing (e.g. an upper or lowerlayer in such a surface), the flaps are folded in on themselves tocreate a cuboid member that extends along the length of each of thesides. This is shown in more detail in FIG. 9F.

FIG. 9F shows how an upper portion 925 or flap of the external casing910 may be folded five times to create a cuboid stiffening member 923. Aforce applied to the upper horizontal surface of the cuboid stiffeningmember 923 is distributed through the vertical sides of the stiffeningmember 923 to the planar surface 921 of the partition 914. The force isthen further distributed from the planar surface 921 to the load bearingelements 924. Although the stiffening members are shown as cuboid in theFigure, other prisms are possible, such as triangular prisms, byconfiguring the number of folds in the upper portion 925. As can be seenin FIG. 9F, the side portions 915 of the partition 914 are securelyaccommodated, e.g. wedged or pinched, between one vertical side of thecuboid stiffening member 923 and the side wall 916. This may act to holdthe partition 914 in place and to prevent access to the internalcompartment 911. It also stops build material and other objects thatcollect on the partition 914 from entering the internal compartment 911.

FIG. 9F also shows how the partition 914 may be used to help secure thestiffening members 923. In the example of FIG. 9F, the planar portion921 of the partition 914 comprises a number of slots 927 (e.g. elongateapertures aligned along a length of the stiffening member). These slots927 receive tabs located on the stiffening members 926 to secure thestiffening members 926 into place and to prevent said members fromunfolding. There may be multiple slot and tab pairs along the respectivelength of the planar portion 921 and the stiffening member 923. In use,and as shown in later Figures, the other two sides of the externalcasing 910 may be folded over the two stiffening members 923 to form anupper surface of the build material container. In other examples,alternate methods of securing the stiffening members, such as tape oradditional members may be used.

FIGS. 10A and 10B are flow diagrams that show methods 1001, 1002 thatmay be applied in association with the partition described in FIGS. 9Ato 9F.

FIG. 10A shows a method 1001 of assembling a build material containerfor a three-dimensional printing system. The build material containermay be the container 901-904 of FIGS. 9A to 9F or a build materialcontainer of a different implementation. The method may be similar, anduse blocks from other methods of assembly, construction, or manufacturediscussed herein.

In FIG. 10A, the method comprises a first block 1005 of obtaining anexternal casing for the build material container. In one case, theexternal casing is obtained by assembling a blank, wherein a blank is afoldable two-dimensional net or template that is used to construct abuild material container. The blank may comprise an unfolded, corrugatedbox or connectable portions of a polymer container. The external casingcomprises base and side portions. The base may comprise flaps that arefoldably coupled to each side portion, wherein the flaps are foldable,e.g. over each other, to generate a base of the external casing. Inother cases, the base may comprise a planar surface foldably coupled toone of the side portions that may be joined to the other side portions.Obtaining an external casing may comprise folding and securing, e.g.with tape or glue, a three-dimensional form of the build materialcontainer. In certain cases, block 1005 may comprise receiving apre-folded or pre-assembled build material container, such as apre-formed box or the like.

FIG. 10A then comprises a block 1015 of arranging an internal reservoirwithin the external casing. The internal reservoir stores build materialand may comprise one of the build material reservoirs described herein,e.g. a reservoir in the form of a box or polymer bag. In the presentcase, the internal reservoir comprises a channel structure, such as anoutlet and/or inlet structure, and a surround. The internal reservoirmay comprise a deformable structure that is affixed or affixable toanother blank. This other blank may then be folded to generate thesurround with the deformable structure inside. The surround may be gluedor taped to form a three-dimensional polyhedral structure. Arranging theinternal reservoir within the external casing, i.e. the assembled buildmaterial container from 1005, may comprise slotting and/or sliding thesurround into the assembled build material container from an open top ofthe container. The build material container may comprise one or moreguide members to facilitate insertion of the surround. These guidemembers may comprise the aforementioned load bearing elements. Inanother case, the build material container may be assembled around thesurround, e.g. where the surround is mounted on a base of the externalcasing or a support structure and the side portions of the blank areassembled around it.

Lastly, FIG. 10A comprises a block 1020 of arranging a partition abovethe internal reservoir and the surround. This may be the partition 914described with reference to FIGS. 9A to 9F or a different form ofpartition. The partition in the present case comprises an aperture toreceive the channel structure of the reservoir. The partition may beplanar or have another structure so as to collect material depositedthereupon. Block 1020 may comprise slotting the aperture over arespective channel structure formed at a top of the build materialreservoir. Following block 1020, the partition forms a lower surface ofan upper compartment of the build material container, wherein the buildmaterial reservoir is held within a lower compartment of the buildmaterial container. Following arrangement, the partition restrictsaccess to a volume of the external casing below the partition. Thepartition is arranged to collect build material during use of thechannel structure. For example, the partition may collect build materialthat is spilt during either supply or filling.

In certain examples, the method 1001 may additional comprise the blockof supplying build material to the internal reservoir via the channelstructure. For example, this may comprise attaching a filling system toan inlet structure of the build material reservoir such that buildmaterial may be supplied to the interior of the reservoir (i.e. fill thereservoir). The filling system may comprise a hose that is coupled tothe inlet structure. Filling may comprise supplying a predeterminedweight or volume of build material to the build material reservoir.Filling may also comprise compacting the build material in the buildmaterial reservoir and/or applying a pressure during supply of the buildmaterial, e.g. so as to accommodate the predetermined weight or volumeof build material intended to be stored therein. Following filling ofthe build material container, any spilt build material may be removed asdescribed below. The channel structure may also be sealed, e.g. using aheat sealer, and/or fitted with tamper-evident mechanisms. Uppersections of the side portions of the external casing may then be foldedover the channel structure of the internal reservoir to form aprotective upper surface of the build material container. This maycomprise folding and sealing upper flaps of a box forming the externalcasing. The external casing may then be wrapped or otherwise protectedfor transport to a location of a three-dimensional printing system.

In one example, arranging an internal reservoir comprises arranging aplurality of internal reservoirs within a support structure, andarranging a planar partition comprises aligning apertures within thepartition with inlets of the plurality of internal reservoirs. Forexample, the support structure may be similar to that shown in FIG. 1H(amongst other Figures). The plurality of internal reservoirs maycomprise a plurality of container cells as described in more detaillater below. For example, the plurality of reservoirs may comprise tworows of internal reservoirs, where each row has two columns, such thatfour internal reservoirs are provided. Each internal reservoir may havea corresponding surround. The partition may therefore be supported oneach surround and/or any load bearing elements. In one case, the channelstructure for each internal reservoir comprises an inlet and outletstructure. In this case, where four internal reservoirs are provided,block 1020 may comprise slotting eight channel structures through aplanar portion of the partition.

As demonstrated in FIGS. 9E and 9F, the method 1001 may comprise foldingupper sections of side portions of the external casing. In one case,this may further comprise folding a first set of opposing upper sectionsto generate upper stiffening members that extend along opposing sides ofthe build material container. This may comprise folding flaps of a blankas shown in FIG. 9F. In this case, flanges of the partition, e.g. sides915 in FIG. 9D, may be secured between the side portions and thestiffening members. This may occur as the stiffening members are foldedover the partition. Once stiffening members have been formed, a secondset of opposing upper sections may be folded over the stiffening membersto form the upper surface of the build material container. For example,this may comprise folding neighboring flaps of the external casing.These neighboring flaps may have themselves a folded portion thatcontacts the surface of the partition to distribute a force applied to acenter of the upper surface to the partition. As shown in FIG. 9F,folding a first set of opposing upper sections may comprise securingtabs located on the upper stiffening members within respective slotsupon the planar partition. For example, a partition may comprise a setof three slots aligned along a length of one side of the externalcasing.

FIG. 10B shows a method 1002 of filling a build material container for athree-dimensional printing system. The method comprises a first block1030 of providing a build material container comprising an internalreservoir. This may comprise performing the method 1001, or supplying adifferently formed build material container, e.g. such as any of thevariations described herein. Block 1035 then comprises supplying buildmaterial to an inlet of the internal reservoir to fill the buildmaterial container. This may comprise attaching a hose or filling tubeto a threaded aperture forming the inlet that is provided within theinternal reservoir, e.g. which is formed within, or affixed to, an uppersurface of the internal reservoir. This filling block may comprise thefilling procedure discussed above. It may continue until a predeterminedquantity of build material has been supplied, e.g. by weight and/orvolume. During block 1035 build material may be spilt on the buildmaterial container. For example, this may occur when fitting and/orremoving a supply hose or tube for the build material. Additionally, ifmultiple reservoirs are used, a last reservoir may be more difficult tofill than a first reservoir, due to a restricted volume within aninternal compartment of the external casing (e.g. other bags may be fullof material). For example, the presence of build material in a givenfull reservoir may exert an outward pressure that is applied to sidewalls of that reservoir, causing deformation outwards as described abovein relation to FIG. 1E and thereby restricting the available volumewithin the internal compartment of the external casing. Hence, buildmaterial may need to be supplied under pressure, which may lead to buildmaterial being spilt when a supply hose or tube is removed. Similarly,residue from a previous fill operation may be present in a supply hoseor tube, or upon or within other components, which may spill orotherwise come to be deposited on the build material container. In thesecases, a tray (e.g. the previously described partition) of the buildmaterial container collects this stray and/or spilt build material andprevents it falling into the internal compartment containing the buildmaterial reservoirs. As such at block 1040, build material within thetray located above the internal reservoir may be removed, e.g. byapplying a vacuum system or via a manual collection. In this case, thetray comprises flanges that abut side walls of the build materialcontainer to prevent stray build material from entering the internalcompartment, e.g. an interior, of the build material container. Withoutthe tray build material may fall within the interior of the buildmaterial container. In this latter comparative case, i.e. without thetray, a build material container may need to be dissembled to clean thecontainer of stray build material container prior to transport. Bysupplying the tray (or partition), build material can be easily andsafely removed.

In one case, following the removal of stray build material, the buildmaterial container is closed to form an outer protective surface. Thismay protect the build material container during transport, e.g. protectthe build material, channel structures and associated supportstructures. In one case, supplying build material to an inlet of theinternal reservoir comprises supplying build material to multipleinternal reservoirs within the build material container.

The examples shown in FIGS. 9A to 9F and 10A and 10B provide a safetycomponent that may be used during filing and/or extraction of buildmaterial. It may be used to prevent dust or residue accumulating withinan interior of the build material container, where it may be difficultto clean and/or remove. This may also be useful to control overflow ofbuild material. It may also be useful when emptying and/or dissemblingthe build material container, e.g. for recycling. It may also avoiddisassembly of the build material container when objects are droppedinto the container. It may also prevent entry or intrusion of foreignelements, e.g. those that could puncture a deformable reservoir orotherwise contaminate build material over time. A partition or tray asdescribed may also be used in conjunction with load bearing orstiffening members to distribute structural loads during filling,transport, and/or supply of build material. For example, structuralloads may be distributed to allow build material containers to bestacked on top of each other. The examples also aid assembly of a buildmaterial container, especially those comprising multiple build materialreservoirs. The examples provide a receptacle for spilt build materialwhich does not form a slope or otherwise allow entry into the interiorof the container.

FIGS. 11A to 11J and FIG. 12 shows examples of an inlet structure for abuild material reservoir, such as a deformable structure or chamber, anda method of supplying build material from a build material reservoir.These examples may increase the efficiency and continuity of the supplyof build material. For example, in certain cases, they may avoidstructures such as “rat-holes” forming in the build material residentwithin the build material reservoir by selectively controlling theingress of gas such as air into the reservoir.

FIG. 11A schematically shows a gas inlet structure 1101 according to anexample. The gas inlet structure 1101 may be used with a deformablebuild material reservoir to facilitate the supply of build material fromthe build material reservoir. The gas inlet structure 1101 may be usedas a channel structure as described in other examples. The gas inletstructure may be used to allow a gas, such as air or an inert gas, intoa deformable structure or chamber of the build material reservoir, e.g.to temporarily increase a pressure within the structure or chamber. Thegas inlet structure may be closed, e.g. to temporarily lower a pressurewithin the structure or chamber when a vacuum is applied, for example byway of an aspiration tube as set out above.

The gas inlet structure 1101 of FIG. 11A first comprises a couplingmechanism 1110 to attach the gas inlet structure to a deformable buildmaterial reservoir. In FIG. 11A, the coupling mechanism 1110 comprises aseries of threads that may be used to couple the gas inlet structure1101 to a corresponding set of threads on the deformable build materialreservoir. For example, if the deformable build material reservoircomprises a polymer bag, the corresponding set of threads may comprise acorresponding coupling mechanism that is heat sealed to an aperture insaid bag, wherein the gas inlet structure 1101 may be screwed into placeupon the bag. In other examples, the coupling mechanism 1110 maycomprise a different structure, e.g. using a different mechanicalcoupling such as interlocking members, using a magnetic coupling, orusing a permanent attachment such as a heat seal.

The gas inlet structure 1101 has an upper aperture 1111 to allow gas toenter the inlet structure and a lower aperture 1112 to allow gas toenter the deformable build material reservoir. In examples, theorientation of these apertures may differ, e.g. the gas inlet structure1101 may be rotated and attached to a side or base of a deformable buildmaterial reservoir.

In FIG. 11A, a passive valve 1113 is located within the gas inletstructure 1101 to selectively allow a gas to enter the deformable buildmaterial reservoir. The passive valve 1113 is configured to operate at apredetermined back pressure. For example, in FIG. 11A, the passive valve1113 may be configured to open and allow gas to flow from the upperaperture 1111 to the lower aperture 1112, i.e. into the deformable buildmaterial structure, when a predetermined pressure differential existsacross the passive valve 1113, e.g. when a pressure below the valve inthe Figure is less than a pressure above the valve in the Figure, e.g.differs by at least a predefined amount. This corresponds to a pressuredifferential between a pressure inside the deformable build materialreservoir and a pressure outside the deformable build materialreservoir, e.g. within an internal compartment of an external casing ofa build material container.

In one implementation, the passive valve comprises an umbrella valve toselectively allow gas such as air to enter the deformable build materialreservoir. This type of valve comprises a diaphragm that moves under aforce applied by a pressure differential. The diaphragm is mounted inits center and as such resembles an umbrella. In other implementationsan alternative valve mechanism may be used, such as a ball or butterflyvalve. Operation of an example umbrella valve is described later withreference to FIGS. 11H to 11J.

FIGS. 11B and 11C are schematic diagrams showing an example buildmaterial reservoir 1102 that has an inlet 1123. This inlet may beimplemented by the gas inlet structure 1101 or another inlet structure.FIGS. 11B and 11C demonstrate how structures such as “rat-holes” mayform in a build material reservoir. The build material reservoir 1102may be a version of one of the build material reservoirs shown in FIGS.1D to 1F. The build material reservoir 1102 is configured to store buildmaterial, e.g. build material as described above, for athree-dimensional printing system.

In FIG. 11B the build material reservoir 1102 has an inlet 1123 thatallows a gas such as air into the reservoir (as indicated by the arrowin the Figure). The build material reservoir 1102 also comprises anoutlet 1122 to allow build material to be supplied from the reservoir toan element of a three-dimensional printing system. For example, buildmaterial may be extracted by applying a vacuum to the outlet 1122. Thevacuum may be applied by an aspiration system of the three-dimensionalprinting system, such as build material transport system 215 in FIG. 2Aor 2B. The outlet 1122 in FIG. 11B comprises an aspiration channel suchthat build material is extracted via an opening at the base of theaspiration channel at the bottom of the build material reservoir 1102.The extraction of build material is represented by an arrow within theoutlet 1122 in the Figure. Although FIGS. 11B and 11C show an aspirationchannel, other configurations may omit these features, e.g. those withan outlet at the base of the build material reservoir.

FIG. 110 shows a structure 1125 forming in build material 1126 duringthe application of a vacuum, e.g. by an aspiration system. In this case,the structure 1125 comprises a tunnel that has formed within the buildmaterial 1126 as build material is extracted under a vacuum. The tunnelis known in the art as a “rat-hole” as it may resemble a tunnel made bya small rodent. The presence of such a tunnel can prevent build materialfrom entering the outlet 1122 and thereby cause a failure of a printingoperation, or of a filling operation of a powder management system orbuild unit of a three dimensional printing system. Once the tunnel formsthe aspiration system begins to extract gas 1127 such as air in an upperpart of the build material reservoir 1102 as well as, or instead of,build material 1126 from the reservoir. Although the tunnel is shown asa single structure, in practice it may form from a number ofmicrostructures that allow a flow of gas from the upper part of thebuild material reservoir 1102 to the outlet 1122.

In a comparative case, a gas inlet without a valve as configured in thepresent examples, allows gas into the build material reservoir 1102 inFIG. 110. As such the supply of build material stalls or stops as eventhough the aspiration system is applying a vacuum, gas rather than buildmaterial is extracted from the build material reservoir 1102.

Certain examples herein, including the gas inlet structure 1101 as shownin FIG. 11A, address the issue of structures forming in the buildmaterial and the supply of build material stalling or stopping bygenerating a series of pressure cycles within the build materialreservoir 1102. When the build material reservoir 1102 comprises adeformable structure, these pressure cycles lead to a cyclicaldeformation in the structure, which help collapse macro and micro fluidchannels or structures, such as rat holes within the build material.This is explained in more detail with reference to FIGS. 11D to 11Gbelow.

FIGS. 11D to 11G show four states 1103 to 1106 of a deformable structure1120 for storing build material for a three-dimensional printing system.The deformable structure 1120 may implement a build material reservoir.As shown in these Figures, the deformable structure 1120 comprises anoutlet 1121 and an inlet 1130. The outlet is connectable to anaspiration system of an element of the three-dimensional printingsystem, to allow build material to be supplied from the deformablestructure 1120 on application of a vacuum by the aspiration system. Theinlet comprises an actuatable valve to selectively allow gas to flowinto the deformable structure 1120. The actuable valve may comprise apassive valve, such as that shown in FIG. 11A, which is configured toopen at a predefined back pressure, i.e. a predefined pressuredifferential. Alternatively, the actuable valve may comprise an activevalve configured to open on supply of an electronic control signal. Inexamples wherein the valve is an active valve, the build material supplycomprises circuitry for opening and closing the valve, as well as apower supply for the circuitry. The valve is actuatable as in it may beselectively controlled or actuated using either active or passivecomponents.

In FIGS. 11D to 11G, the outlet 1121 forms an upper part of anaspiration channel 1122 that extends along a length of the deformablestructure 1120. As described previously, the aspiration channel 1122 maycomprise a pipe or tube that extends within the interior of thedeformable structure 1120 to enable build material to be efficientlyextracted. The aspiration channel 1122 has an opening 1131 at a base ofthe deformable structure. In FIG. 11D, the base of the deformablestructure 1120 is polyhedral in order to maximize build materialextraction. Although, FIG. 11D shows a polyhedral base and an aspirationchannel, other configurations may omit these features, e.g. those withan outlet at the base of the build material reservoir, while stillapplying an inlet as described in the present examples.

As shown by the arrows in FIG. 11D, during application of a vacuum tothe outlet 1121, build material is transported from the deformablestructure 1120. In the example of FIG. 11D this is through the opening1131 and up the aspiration channel 1122, to the outlet 1121. The term“vacuum” as used herein means a pressure that is substantially lowerthan a normal pressure within the deformable structure and buildmaterial container that allows build material to be extracted via theoutlet 1121. A vacuum may be applied by a build material transportsystem such as 215 in FIGS. 2A and 2B. In practice, a mixture of buildmaterial and the gas within the deformable structure 1120 may beextracted, wherein in normal operation this mixture is mainly buildmaterial.

During normal operation, as shown in FIG. 11D, the inlet 1130 isinitially closed. While build material is being successfully extracted,a pressure within the deformable structure, e.g. in an empty portion ofthe deformable structure 1120, slowly decreases as a volume of buildmaterial is removed from the structure. The pressure within the emptyportion is above a predefined pressure threshold for operation of theactuatable valve within the inlet 1130. The empty portion comprises anupper portion of the deformable structure 1120 shown in FIG. 11D. Theportion is “empty” as in it does not contain build material; however, itmay contain a gas such as air or an inert gas.

If a structure 1125 forms in the build material 1126 that fluidicallycouples the empty portion to the aspiration system applying the vacuumthen the pressure in the upper empty portion may rapidly decrease as gasis removed from the empty portion. As shown in FIG. 11E this reductionin pressure in the empty portion leads to a deformation of thedeformable structure 1120. In particular, sides 1135 of the deformablestructure 1120 may deform inwards. For example, if the deformablestructure 1120 comprises a polymer bag, then sides of the bag may besucked inward.

In certain examples, the deformable structure 1120 may be attached to asupporting surround, e.g. as described with reference to previousexamples. In this case, the deformable structure 1120 may deform withinthe constraints imposed by attachments to the supporting surround, e.g.the structure may still be retained in places to the supporting surroundbut may deform inwards in sections between these places. In other cases,a surround may be omitted.

As shown in FIG. 11E, a reduction in pressure in the deformablestructure 1120 deforms at least a portion of the sides of the structureand compresses the build material within. In some examples, the entiretyof the sides of the structure 1120 are deformed, as shown in FIGS. 11Eand 11F. In other examples, portions of the sides of the structure 1120are deformed. For example, the structure 1120 may deform in emptyregions of the structure but not in regions below the level of buildmaterial in the structure 1120. The degree of deformation may depend onthe fill level of the structure 1120. This also leads to compression ofbuild material surrounding the structure 1125. The structure 1125 isthus also compressed as shown by 1132 in FIG. 11E.

FIG. 11F shows that as the pressure reduces further in the deformablestructure a predefined threshold pressure is reached. For example, thismay comprise a predefined pressure differential across the inlet 1130 ora measured pressure, either within the deformable structure 1120 itselfor via the aspiration system that is coupled to the outlet 1121. In FIG.11F, at the predefined threshold pressure, the valve in the inlet isopened as shown by the arrow. The valve may be opened actively bysupplying an electronic control signal to actuate the valve or passivelyby a component such as a membrane within the valve changing shape and/orsize to allow gas to flow into the empty portion of the deformablestructure 1120. As shown in FIG. 11G, allowing gas flow into thedeformable structure 1120 deforms the sides 1137 of the structureoutwards, i.e. back towards a default or relaxed state. This thendecompresses the build material within the deformable structure. Thecycle of compression and decompression collapses the original structure1125, as shown by 1136 in FIG. 11G. As gas flows into the deformablestructure 1120, the pressure increases and the valve once again closes,either passively or through deactivating the electronic control signal.Build material can this continue to be successfully extracted.

The sequence shown in FIGS. 11D to 11F provides a “bellows” effect on atleast portions of the deformable structure that collapses macro andmicro structures that form in build material within a build materialreservoir. The changes in pressure enabled by the actuatable valve inthe inlet 1130 in the deformable structure radially compress and crushthese structures. As build material is removed from the deformablestructure, the pressure inside the structure decreases (i.e. a vacuumwithin the structure increases). The pressure decrease is enabled by theclosing of the valve. When the valve is opened the pressure inside thestructure increases (i.e. the vacuum within the structure decreases).Expansion of the deformable structure enables the macro and microstructures within the build material to collapse into the bottom of thedeformable structure. This cycle may be repeated multiple times duringsupply of build material. When a passive valve is used, the cycle isinitiated automatically during supply. When supply of build material iscomplete, the aspiration system may be switched off such that a vacuumis no longer applied to the outlet 1121. In this case, gas may flow intothe bag via the outlet 1121 to reinflate to a default or relaxed state.This default or relaxed state may be configured based on a shape and/orsize of any supplied surround. In certain examples, the deformablestructure may have an elasticity such that stretching of at least oneside wall during deformation inwards is opposed by a tendency of thestructure to return to a relaxed state. This may operate in combinationwith attachment to the surround, e.g. such that deformation andstretching occurs between the attachment points.

FIGS. 11H to 11J show how an example passive valve within a gas inletstructure 1150, 1160 may be actuated during the cycle shown in FIGS. 11Dto 11G. For example, this may comprise a version of the valve installedwithin a gas inlet structure such as 1101 in FIG. 11A. FIGS. 11H and 11Iare schematic cross-sections, while FIG. 11J is a cross-section of anexample inlet structure.

The gas inlet structure 1150 of FIGS. 11H and 11I comprises a casing1151, wherein a coupling mechanism 1110 is configured to couple theinlet structure 1150 to a build material reservoir. The couplingmechanism may for example be in the form of a series of threads formedwithin, i.e. on the exterior of, the casing, or another form ofmechanical coupling. Alternatively or additionally, the inlet structure1150 may be coupled to the build material reservoir by way of adhesive.A passive valve in the form of an umbrella valve 1152 is mounted withinthe casing 1151. The umbrella valve 1153 comprises a central member ortail that may be inserted into a bore within an annular valve supportmember 1153 mounted within the casing 1151. In certain cases, theannular valve support member may comprise part of the casing. A convexdiaphragm of the umbrella valve may be supported upon the annular valvesupport member 1153. The convexity of the diaphragm and/or a preloadingof the diaphragm may be selected to configure a predeterminedback-pressure at which the valve opens. The umbrella valve may be formedfrom an elastomer. The gas inlet structure 1150 of FIG. 11H alsocomprises a filter 1154 to restrict access to the deformable buildmaterial reservoir. The filter 1154 may be circular and may comprise acircle of foam together with a retainer to hold the foam against anupper surface of the casing 1151. An induction seal (not shown) may beapplied to the top of the casing 1151. The annular valve support member1153 may be placed after the retainer within the casing 1151.

FIG. 11I shows the gas inlet structure 1150 when the passive valve isactuated at a predetermined back pressure. In this case, the diaphragmelastically deforms to allow gas to flow through the inlet structure1150. FIG. 11J shows an implementation 1160 of gas inlet structure 1150as threaded onto a corresponding mounting 1156 within the build materialreservoir. The build material reservoir in this case comprises adeformable structure comprising a polymer bag with threaded aperturesfor the gas inlet structure.

In certain examples, a gas inlet structure as described above may formpart of a build material container as described herein. For example, abuild material container for a three-dimensional printing system maycomprise an external casing and at least one internal reservoir forholding build material. Each internal reservoir may be positioned withinthe external casing and may comprise an outlet structure through whichbuild material is supplied when a vacuum is applied, and an inletstructure with an airflow valve, wherein the airflow valve of eachinternal reservoir is selectively actuatable to collapse and re-inflateeach reservoir during supply of build material.

FIG. 12 shows an example method 1201 of supplying build material for athree-dimensional printing system. At the start of the method 1201, aninlet of a deformable or collapsible structure storing build material isclosed. This may be because a pressure within the structure is above apredetermined threshold or because an electronic signal to open a valveof the inlet is not supplied (an electronic signal to close the valvemay be supplied at this stage). At block 1220, a vacuum, i.e. a lowpressure source, is applied to an outlet of the deformable structure,while the inlet is closed, to extract build material from the deformablestructure to supply the three-dimensional printing system. This vacuummay be applied by a build material transport system 215 as describedwith reference to FIGS. 2A and 2B. Lastly, at block 1230, while thevacuum is applied to the outlet, a pressure difference is caused throughapplication of the vacuum within the deformable structure to cause avalve of the inlet to allow gas flow into the deformable structure. Thevalve may be a passive valve or an active valve. The valve may beconfigured to open at a predefined back-pressure. For example, a passivevalve such as an umbrella valve may have a resistance set to open at thepredefined back-pressure. An active valve may be opened in response toan electronic control signal in response to a detection by a pressuresensor of the pre-defined back pressure, wherein the active valve isclosed in absence of the electronic control signal. This method may beapplied to implement the cycles shown in FIGS. 11D to 11G using one ofthe aforementioned gas inlet structures.

In one case, the method comprises measuring a pressure in a vacuumsystem coupled to the outlet and activating the active valve at apredefined threshold pressure. In another case, the method comprisessupplying the electronic control signal to open the active valve atpredefined time intervals. The latter case may be applied in addition,or instead of, a case where a pressure is measured. In the latter case,the predefined time intervals may be configured such that structures donot form in the build material.

In one example, the gas inlet valve described in the present examplesmay be used to help remove the deformable structure from a surround whena build material container needs to be dismantled for recycling. Forexample, if the vacuum is applied to the outlet after the build materialhas been extracted, because the valve is initially closed, e.g. until apredefined back pressure is reached, the side of the deformablestructure may deform inwards such that they become detached from thesurround. The deformable structure may thus be easily removed from thesurround for recycling. In this case, and in other situations, a passivevalve such as that shown in FIGS. 11A and 11H to J may prevent buildmaterial from exiting the inlet of the deformable structure, e.g. duringcycles of expansion and contraction of the sides of the structure.

Certain examples described with reference to FIGS. 11A to 11J and 12address a case where an air passageway forms in the build material in abuild material bag such that air, rather than build material, isextracted from the bag. Certain examples introduce a selective valvewithin an air inlet. This valve is actuatable at a given pressure. Whena “rathole” forms the air inlet is initially closed. As mainly airrather than mainly build material is extracted by the processingstation, the pressure inside the bag decreases and the bag deformsinwards. When the given pressure is reached, air is allowed through theair inlet to re-expand the bag. This concertina or bellows effectcollapses the “rathole” allowing build material to again be extractedunder the vacuum. This operation may be cycled multiple times duringoperation. As build material is extracted then the cycles may becomemore frequent, e.g. as a larger proportion of gas is extracted alongwith the build material due to the increased size of the empty volume ofthe deformable structure.

FIGS. 13A to 13C present example build material containers 1301-1303.These build material containers are adapted to contain multiple buildmaterial reservoirs or “container cells”.

FIG. 13A shows schematically a build material container 1301, comprisingan external casing 1305 and a single deformable reservoir 1306, forexample as described in more detail above. The reservoir has an outlet1307 to supply build material stored within the deformable reservoir.The reservoir has a lower vertex, with lower sides leading to the vertexbeing at an angle 1308. The vertex may comprise a vertex of a pyramid,cone shape or similar polyhedron. As explained above, the presence ofsuch a vertex enables build material to be efficiently extracted fromthe build material reservoir 105, e.g. the build material collectsaround the vertex in the interior of the outer structure 120 where itmay be extracted using an aspiration channel (not shown). The angle 1308may be an “avalanche” angle, or angle of repose, i.e. an angle at whichbuild material falls down, under gravity, the lower sides of the buildmaterial reservoir 105 towards the vertex. The angle of repose may be aconstant based on at least one of a design of the build materialreservoir, type of build material, and material of side walls of thebuild material reservoir. The “avalanche” angle may depend on acoefficient of friction for the side walls and a diameter of a particleof build material.

FIG. 13B shows schematically a build material container 1302, comprisingan external casing 1305 and a plurality of reservoirs 1309 a, b withinthe external casing 1305. Each reservoir 1309 a, b has an outlet 1310 a,b to supply build material stored within their respective reservoirs,for example as described in more detail above. In some examples, theoutlet structures are selectively sealable. The reservoirs may bedeformable reservoirs, as described in more detail above.

Each reservoir 1309 a, b has a vertex, with lower sides leading to thevertex being at the same angle 1308 as shown in FIG. 13A. The reservoirs1309 a, b may have common dimensions. It should be noted that althoughFIG. 13B shows the same lower side angle for each reservoir 1309 a, b,in other examples the lower side angles may differ between reservoirs.In examples, each reservoir 1309 a, b comprises an aspiration channelcoupled to the outlet 1310 a, b and extending along the length of thereservoir 1309 a, b.

As can be seen from FIGS. 13A and 13B, despite having the same lowerside angle 1308 and thus correspondingly similar efficiencies of buildmaterial extraction efficiency, the plural reservoirs 1309 a, b of thecontainer 1302 occupy a greater proportion of the container 1302 thanthe single reservoir 1306 of container 1307. As such, for a givencontainer size, the use of plural reservoirs allows a greater quantity(i.e. volume) of build material to be contained, whilst keeping the samelower side angle 1308 and thereby not compromising efficiency ofextraction. For example, if the build material reservoirs are made of asimilar material and contain similar build material, the “avalanche”angle may be within a common range for both FIGS. 13A and 13B.

The use of plural reservoirs 1309 a, b also allows a given reservoir1309 a, b to remain sealed until used, for example as described above inrelation to FIG. 6I. This reduces the length of time that a givenreservoir 1309 a, b is open to the atmosphere, thereby improvingpreservation of build material. For example, preservation may beimproved by preventing admission of humidity in to the build materialand/or oxidation of metal powder build material.

In some examples, the plurality of deformable reservoirs 1309 a, bcontain a common build material. In addition to increasing the volume ofbuild material in the container, this allows the container to beconnected to a three-dimensional printing system capable of receivingbuild material from two or more reservoirs 1309 a, b, for example by wayof a pair of build material supply hoses connected to the outlets 1310a, b. One hose can thus be disconnected from an outlet 1310 a, b of anempty reservoir 1309 a, b and connected to an outlet 1310 a,b of a fullreservoir 1309 a, b, while the other hose is connected to a non-emptyreservoir 1309 a, b. In this manner, uninterrupted printing may beperformed.

Alternatively, at least two of the plurality of deformable containersmay contain different building materials. This allows switching betweensuch building materials, which may for example produce differentmechanical properties, or finishes or colors, in a printed article.

In some examples, the plurality of deformable reservoirs 1309 a, b arearranged to form a plurality of columns and a plurality of rows withinthe external casing 1305, for example as described above in relation toFIGS. 3D and 3E.

In examples, each deformable reservoir 1309 a, b comprises an inletstructure to allow at least one of build material and gas to flow intothe reservoir.

FIG. 13C shows schematically an example build material container 1303,comprising an external casing 1305 and a plurality of deformablereservoirs 1309 a, b as described above. Each deformable reservoir 1309a, b comprises an aspiration channel and a surround, wherein a base ofeach surround comprises a vertex formed at an end of the aspirationchannel. As described above, the base comprises at least one lowerangled surface.

The build material container 1303 further comprises a support structure1311 to accommodate the vertices, and to support the lower angledsurfaces, of the plurality of surrounds. The support structure 1311 maybe configured as described above in relation to FIGS. 1H and 11.

FIG. 13D shows schematically a support structure 1311 for a buildmaterial container 1303. The support structure 1311 comprises aplurality of polyhedral indentations 1315 a, b in an upper portion ofthe support structure 1311. Each polyhedral indentation 1315 a, b isconfigured to receive a base of a container cell for the build materialcontainer. In some examples, the polyhedral indentations are regularlyspaced in the upper portion.

A base 1316 of the support structure is arranged to rest on a planarsurface, such as the bottom of the build material container 1303. Forexample, the support structure 1311 may be dimensioned to beaccommodated within a base of a cuboid build material container 1303.

FIG. 14 presents a flow chart of a method 1401 of filling a buildmaterial container, according to an example. At block 1405, the method1401 comprises providing a group of deformable build material reservoirsin a common housing. At block 1406, the method 1401 comprises fillingeach of the group of deformable build material reservoirs in the commonhousing with build material. At block 1407, the method 1401 comprises ablock 1407 of sealing the group of deformable build material reservoirs.This may comprise a heat, vacuum and/or adhesive seal, amongst others.

The method 1401 may comprise folding upper sections of the commonhousing over the sealed deformable build material reservoirs to protectsaid reservoirs during transport, for example as described above inrelation to FIG. 5.

In some examples, the method 1401 further comprises unsealing an outletof one of the deformable build material reservoirs, and coupling anaspiration system of a three-dimensional printing system to the outletto extract build material via the outlet, for example as described abovein relation to FIG. 6I.

According to an example, there is provided a build material containerfor a three-dimensional printing system. The build material containercomprises a plurality of reservoirs (i.e. container cells) to storebuild material. Each container cell comprises an outlet structure tocouple the container cell to the three-dimensional printing system, andan aspiration channel coupled to the outlet structure and extendingalong the length of the container cell. A base of the container cellcomprises a vertex formed at an end of the aspiration channel, the basecomprising at least one lower angled surface. The container furthercomprises a support structure to accommodate the vertices, and tosupport the lower angled surfaces, of the plurality of container cells.

FIGS. 15A and 15B show cross sections of a build material container 1501implementing multiple above-described examples. FIG. 15B represents aview rotated 90 degrees about a vertical axis of the container 1501.Build containers may similarly implement any combination of the examplesdescribed herein.

The container 1501 comprises a plurality of build material reservoirs1502 a, b, each having a corresponding aspiration channel 1503 a-c andinlet and/or outlet structures 1504 a-c as described above for examplein relation to FIGS. 1D to 1F and/or 11A to 11J. Another channelstructure may be present behind the viewable structures in the Figure.The channel structures 1504 a-c are exposed by removal of structurallyweakened portions of the external casing, as described above in relationto FIGS. 6A to 6I. For example, FIG. 15A shows apertures in an uppersurface of the build material container 1501 where portions have beenremoved above. The reservoirs 1502 a-c are supported by a supportstructure 1507, for example as described above in relation to FIGS. 1Hand 11 and/or 13C and 13D. In practice, the support structure maycomprise a plurality of support structures such as 1507 to provide adesired height for the build material reservoirs 1502. FIG. 15B alsoshows inlet structures 1509 a, c that are arranged next to the outletstructures 1504 a, c. In FIG. 15B the outlet structures are shown withan upper lid open and pivoted to one side to allow access. In FIG. 15B asecond set of stiffening members 1510 are also visible—these comprisethe folded edges of the front and rear flaps for the external casing ofthe build material container 1501.

As described previously, an example build material container 1501 may be1.5 m tall (i.e. a length in a z dimension as indicated in the Figures),with a length of 1 m (i.e. a length in an x dimension as indicated inthe Figures) and a width of 0.75 m (i.e. a length in a y dimension asindicated in the Figures). A height of examples may generally be withina range of 1 to 2 m and widths and lengths may be selected from a rangeof 0.5 to 2 m. A width and length of the build material container 1501,e.g. dimensions of a horizontal cross section, may have equal ordifferent values. In an example with four internal reservoirs arrangedas shown in FIG. 16, each internal reservoir may have a length (in xdimension) of around 50 cm, a width (in a y dimension) of around 37.5cm, and a height (in a z-dimension) of around 120 to 140 cm. The supportstructure may be 30 to 40 cm high with dimensions to fit within the baseof the build material container 1501. The support structure may have aheight of around 5 to 20 cm in its lowest portion to accommodate avertex of the build material reservoir. An angle of repose may be withinthe range of 50 to 70 degrees.

The container 1501 further comprises columnar load-bearing elements 1505a-c, and an upper compartment comprising folded stiffening members 1506a, b, as described above in relation to FIGS. 3A to 3C. The container1501 also comprises a partition 1508, as described above in relation toFIGS. 9A to 9F.

The container 1501 is mounted on a pallet 1511, such as a wooden pallet.The pallet may have a length and a width (i.e. x and y dimensions) equalto the external casing, e.g. 1×0.75 m. It may have a standard height,e.g. 15 to 20 cm. In some examples, the pallet 1511 is integral to thebuild material container 1501. In other examples, the pallet 1511 is aseparate component, attached to the container 1501 for example byadhesive or straps. The pallet 1511 simplifies transport and storage ofthe container 1501.

In some examples, following use the container 1501 is separated into itscomponent parts, packaged and returned to a build material supplier forrefilling.

FIG. 16 shows schematically an exploded perspective view of a buildmaterial container 1601 according to an example. This view demonstratesone way in which a build material container may be constructed. Thecontainer 1601 comprises an external casing 1602. A support structure(not shown) may be present within the external casing 1602, for examplethis may be inserted following construction of the external casing 1602.Within the external casing 1602 are columnar load-bearing elements 1603,for example as described above. The casing 1602 further comprises upperflaps 1603 a, b with foldable portions, the foldable portions being forproducing stiffening members for transferring load to the columnarload-bearing elements 1603 as described above.

The container 1601 further comprises a plurality of build materialreservoirs 1605, as described above. The columnar load-bearing elements1603 may be used as guides when inserting the reservoirs 1605 into thecasing 1602, to aid in accurate positioning.

The container 1601 comprises a partition 1607, the partition being toform an upper surface of the internal compartment and thereby to collectbuild material during use of the channel structure as described in moredetail above.

The preceding description has been presented to illustrate and describecertain examples. Different sets of examples have been described; thesemay be applied individually or in combination for a synergetic effect.This description is not intended to be exhaustive or to limit theseprinciples to any precise form disclosed. Many modifications andvariations are possible in light of the above teaching. It is to beunderstood that any feature described in relation to any one example maybe used alone, or in combination with other features described, and mayalso be used in combination with any features of any other of theexamples, or any combination of any other of the examples.

What is claimed is:
 1. A build material container for athree-dimensional printing system, comprising: an external casing; aninternal compartment within the external casing, comprising: a reservoirto store build material, the reservoir having a channel structure; asurround that encloses the reservoir; and a partition within which thechannel structure is mounted, the partition forming an upper surface ofthe internal compartment and being independent from the external casingand the surround, wherein the partition restricts access to the internalcompartment, and wherein the partition is arranged to collect buildmaterial during use of the channel structure.
 2. The build materialcontainer of claim 1, comprising: a plurality of reservoirs having aplurality of respective channel structures, wherein the partitionsupports the plurality of channel structures within a set of respectiveapertures.
 3. The build material container of claim 1, wherein thepartition comprises: a planar portion, a plurality of side portions thatproject upwards, wherein the side portions abut side walls of theexternal casing.
 4. The build material container of claim 3, wherein theplanar portion comprises a lower surface of an upper compartment of theexternal casing and the side portions are accommodated between the sidewalls of the external casing and stiffening members of the uppercompartment.
 5. The build material container of claim 1, wherein thepartition comprises a plurality of slots to receive respective tabs ofthe stiffening members.
 6. The build material container of claim 1,wherein the channel structure comprises at least one of an inlet and anoutlet for the structure.
 7. The build material container of claim 1,comprising: a plurality of columnar load-bearing elements arranged belowthe partition, wherein load is distributed to the load-bearing elementsthrough the partition.
 8. A method of assembling a build materialcontainer for a three-dimensional printing system, the methodcomprising: obtaining an external casing for the build materialcontainer, the external casing comprising base and side portions;arranging an internal reservoir within the external casing, the internalreservoir storing build material and comprising a channel structure anda surround; and arranging a partition above the internal reservoir andthe surround, the partition comprising an aperture to receive thechannel structure of the reservoir, including: arranging the partitionto form a lower surface of an upper compartment of the build materialcontainer, arranging the partition to restrict access to a volume of theexternal casing below the partition, and arranging the partition tocollect build material during use of the channel structure.
 9. Themethod of claim 8, comprising: supplying powdered build material to theinternal reservoir via the channel structure; and folding upper sectionsof the side portions over the channel structure of the internalreservoir to form a protective upper surface of the build materialcontainer.
 10. The method of claim 8, wherein: arranging an internalreservoir comprises arranging a plurality of internal reservoirs withina support structure, and arranging a partition comprises aligningapertures within the partition with inlets of the plurality of internalreservoirs.
 11. The method of claim 9, wherein folding upper sections ofthe side portions comprises: folding a first set of opposing uppersections to generate upper stiffening members that extend along opposingsides of the build material container, including securing flanges of thepartition between the side portions and the stiffening members; andfolding a second set of opposing upper sections over the stiffeningmembers to form the upper surface of the build material container. 12.The method of claim 11, wherein folding a first set of opposing uppersections comprises: securing tabs located on the upper stiffeningmembers within respective slots upon the partition.
 13. A method offilling a build material container for a three-dimensional printingsystem, the method comprising: providing a build material containercomprising an internal reservoir; supplying build material to an inletof the internal reservoir to fill the build material container; andremoving stray build material within a tray located above the internalreservoir during said supplying, said inlet being located within anaperture of the tray, the tray comprising flanges that abut side wallsof the build material container to prevent stray build material fromentering an interior of the build material container.
 14. The method ofclaim 13, comprising: following removing stray build material, closingthe build material container to form an outer protective surface. 15.The method of claim 13, wherein supplying build material to an inlet ofthe internal reservoir comprises supplying build material to multipleinternal reservoirs within the build material container.